09.08.2012 - Released
09.08.2012 - BURST BUILD: Rod of Ages changed to Doran's Ring+ Haunting Guise, HYBRID BUILD: Rod of Ages changed to rylais.
10.08.2012 - added SKILL ORDER and TOP LANE MATCHUP sections + Nasus matchup
14.08.2012 - BURST BUILD: Haunting Guise changed to rylais, Mordekaiser matchup, formatting changes.
20.08.2012 - small changes. Grammar spell check (omg - what mistakes I did! LOL). Forgive me - I'm not native english.
21.08.2012 - added Jax matchup, better skills description.
22.08.2012 - added "Mid game" section
23.08.2012 - added Kennen matchup, updated "Mid game" with ganking paths

Thigs that will be added soon:
-End game
-More matchups
-Jungling
-Video of me playing Diana with every playstyle (Mid Burst, Top Burst, Hybrid, Jungler)

So far this guide is for Diana MID and TOP lanes.

WHY:
First of all I know that at the moment Diana is understood more as mid/jungle champ, but I'm mainly top player so I try also to play her top.
"But why you want to play melee AP assassin at top" you may ask? "It's not working!". "Too squishy!". "No sustain!". "There was already Fizz - you are shut down early very easily".
Also Diana is AP assassin, she should do "tons of damage", but all AP top to survive build tanky ( Cho'Gath, Malphite, Galio, etc.) or at least they can farm cause they are ranged ( Rumble, Kennen, Vladimir, etc.).
So why?
I want to play her cause I fall in love with her <3 <3 <3 :D
And I want to find a way to efficiently play her on every possible position.

Week later after writing above: After playing more than 50 games with Diana I can say that she is viable in all 3 spots: mid/top/jungle.

DIANA:

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She has great graphics - swaying hair, epic weapon, great skill animations. She is not another flat champ with not interesting story - she is dark, cruel Moon assassin, bad mirror reflection to Solari Leona. She has great, long, funny, epic speeches ("...and they DIE..!" lol). Not like some other boring ones, for example my precious Riven (but there isn't any better than "baker" of Panth hehe...) She has 4 AOE (AreaOfEffect) skills (remember about passive). She has AOE CC (slow + pull). She has very long range Ultimate (jump+dmg). She is like Akali but with all AoE skills instead of single target mostly (she lacks of invisible shroud instead). She has great music in game starting menu - best there was ever :) She can carry solo - yes she is powerful - good champ for solo queue.

Mid BURST:

I go 21/0/9 because:

• 21/9/0 would give you more defense buy you don't want to engage in fight early - you want to poke enemy/farm with Diana from far away. And later it doesn't make much difference opposite to mana, mana regen and run speed form UTILITY tree.
• Those 2 point in Butcher are for better last hitting - better to AutoAttack than to waste mana on minions.
• I put 1 point in Swiftness and 1 point in Runic Affinity cause you will be getting blue buffs from your jungler (you always have to get it for mana regen and cooldown reduction).
  

Top BURST:

I go 21/0/9 because:

• 21/9/0 would give you more defense buy you don't want to engage in fight early (especially in top lane where as your enemy you mostly have sustain champions which will regenerate fast you small, early damage) - you want to poke enemy/farm with Diana from far away. And later it doesn't make much difference opposite to mana, mana regen and run speed form UTILITY tree.
• Those 2 point in Butcher are for better last hitting - better to AutoAttack than to waste mana on minions.
• I put 2 points in Swiftness instead of 1 point in Swiftness and 1 point in Runic Affinity cause you are not jungler nor mid champ and you won't be taking lot of buffs.

Top HYBRID (aka. test/fun-troll build):

I go 9/11/10 because:

• You can sustain more having this 11 points in defense tree - to survive this hard early stage where you are squishy as hell and don't have damage to trade with enemy.
• You want 10 points in Utlity tree for mana regen and especially those 3 points in Swiftness for later chase ability - very important in assassin hybrid style build.
• Those 2 point in Butcher are for better last hitting - better to AutoAttack than to waste mana on minions.

Mid BURST:

• Greater Mark of Magic Penetration - 8,55 MagicPenetration - As Diana is magic damage champion. Mid enemy champions have low magic resists so you lower it even more. Later with Sorcerer's Shoes and Abyssal Mask you will be close to true damage - best marks you can get for those slots
  
• Greater Seal of Vitality - 174,96 HP - For this minimum advantage in lvl 6 fight against you AP mid champs. You should have 2xDoran rings already (you have enough damage already) so this additional HP can help you survive damage trade and win in this battle.
  
• Greater Glyph of Scaling Ability Power - 27,54 MR - For this minimum defense against AP champs
  
• Greater Quintessence of Ability Power - 14,85 AP - For this early damage boost.

Top BURST:

• Greater Mark of Magic Penetration - As Diana is magic damage champion. Top enemy champion will go some magic resist against you so it's good idea to work something against - best marks you can get for those slots
  
• Greater Seal of Armor - For this minimum defense against AD champs. You want to avoid early dmg at any cost, but sooner or later they will get ya :)
  
• Greater Glyph of Scaling Magic Resist - For this minimum defense against AP champs
  
• Greater Quintessence of Ability Power - For this early damage boost.

Top HYBRID (aka. test/fun-troll build):

• Greater Mark of Magic Penetration - As Diana is magic damage champion. Top enemy champion will go some magic resist against you so it's good idea to work something against - best marks you can get for those slots
  
• Greater Seal of Armor - For this minimum defense against AD champs. You want to avoid early dmg at any cost but sooner or later they will get ya :)
  
• Greater Glyph of Scaling Magic Resist - For this minimum defense against AP champs
  
• Greater Quintessence of Ability Power - For this early damage boost.

Mid BURST:

STANDARD:

• Flash - obvious. When you enter a teamfight and you realize that they focused you - flash out. After that wait a little (skills CD)... and go back to rape them :) Anyways - always take this skill as Diana doesn't have any escape tool...
• Ignite - for additional dmg and especially for healing bastards (hi Vladimir!)

OPTIONAL:

• I don't take into consideration any other summoner spell than Flash & Ignite for mid lane. It's so simple to me. Only those 2 are chosen & tested by millions of summoners around the world and are taken in 99% cases. Only Flash will help you avoid often ganks on mid lane and only Ignite will give you win in 1v1 battle on this most important lane.

Top BURST & HYBRID:

STANDARD:

• Flash - obvious. When you enter a teamfight and you realize that they focused you - flash out. After that wait a little (skills CD)... and go back to rape them :) Anyways - always take this skill as Diana doesn't have any escape tool...
• Ignite - for additional dmg and especially for healing bastards (hi Vladimir!)

OPTIONAL:

• Teleport (instead of ignite) - you can make easy kills sometimes from it ( Teleport in team fight bot). Take this especially if you play with friends who can call you in correct time.
• Heal - only good for matches where enemy team has a lot of AoE damage champs (with AoE ultimates, skills, etc.). I take it for example in matches against Singed - I know my team will always be running too much in his poison and I can save them with Heal. Even after nerf I never regreted when I took this skill.

Passive: Moonsilver Blade
Diana gains 20% additional attack speed. Every third strike cleaves nearby enemies for 20 / 25 / 30 / 40 / 50 / 65 / 80 / 95 / 110 / 125 / 140 / 155 / 175 / 195 / 215 / 240 / 265 / 290 (+0.6 per ability power) additional magic damage.

Explanation:

• This cleave every third attack makes...hmmm... TONS OF DMG! (I know - not funny anymore)
• It makes additional dmg even to towers (50% but always...). To all enemies around you. It scales with AP and your level. It's crazy.
• You can skip it, don't stress it but I prefer to use it by giving Diana some AS (attackSpeed) items and see "WTF! OP! NERF HER!" cry from enemy team.
• BTW thx riot for not allowing us to know which attack will proc - no icon like for other champs like Annie, Kennen, etc. - you can see it only by the glow on Diana - hard to see it especially in 5v5 battles

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Q: Crescent Strike
Unleashes a bolt of lunar energy in an arc dealing 80/125/170/215/260 (+0.8) magic damage.
Afflicts enemies struck with Moonlight, revealing them for 3 seconds.
Cost 55 Mana
Range 25000
Cooldown: 10 Seconds

Explanation:

• This is AoE ability that hits everything on her path. So before it lands on target area it also damages everything it flies through. The only problem is that path of this projectile is rounded :) So depending on direction you are hitting it can be harder to hit the target. It will take some time till you will get used to it.
• Very short CD (coolDown) - remember to use this skill in fight. Funny? No, because I cought myself many times that I didn't use it cause I'm not used to have skills with so short CD. Remember to use it as a poke before a teamfight.
• Great AP ratios.
• Long range.
• on hit it reveals target for 3 seconds. Great for checking bush etc. But it does not reveal stealthed units :(
• Later when you learn how to use it you will be able to hit enemy champion and farm at the same time - just put yourself in proper position to that.

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This is how Q projectile looks like:

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This is max Q skill range (pretty big):

You can avoid hiting minions, but attack enemy. Very helpfull when you don't want to push:

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This is Q glow when enemy got hit. You can see them even if they are hiden in bush:

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W: Pale Cascade
Creates three orbiting spheres that explode on contact with enemies dealing 20/36/52/68/84 (+0.2) magic damage. Lasts 4 seconds.
Also gains a temporary shield that absorbs 55/80/105/130/155 (+0.45) damage. This shield is refreshed if the third sphere detonates.
Cost 60/70/80/90/100 Mana
Range 750
Cooldown 10/10/10/10/10 Seconds

Explanation:

• Double shield - you activate it, you get shield + 3 orbs circling around you. If all 3 orbs are detonated (minions, enemy champs) you get another shield. Cool, no? :) It can mislead enemy sometimes for example in under-tower situation they think they need to 1 last hit you but you get another shield. Frustrating.
• Those 3 circling orbs make AoE dmg on contact - me like it :)
• People use this before entering the battle - I think in most cases it's a mistake. You should use it after you enter battle with Lunar Rush to some carry and just after you hit Moonfall. This way you make that everyone pulled to you with Moonfall gets hit by your Pale Cascade and only this way you make maxim possible damage.

This is how W skill looks likel:

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It makes AOE damage:

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E: Moonfall
Draws in all nearby enemies and slows them by 35/40/45/50/55% for 2 seconds.
Cost 70 Mana
Range 450
Cooldown 26 Seconds

Explanation:

• Slows nearby enemies and pulls them to you.
• Good range - something like Darius pull, but it works in all directions.
• Don't use it when you escape :) (it slows, but first you pull enemy to you - may be enough to last hit you)

This is the range of E skill:

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This is how E skill looks like:

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R: Lunar Rush
Becomes the living embodiment of the vengeful moon, teleporting to an enemy and dealing 100/160/220 (+0.6) magic damage.
Lunar Rush has no cooldown when used to teleport to an enemy afflicted with Moonlight.
Cost 50/65/80 Mana
Range 900
Cooldown 20/16/12 Seconds

Explanation:

• Long range (longer than Akali) jump.
• Low (for an ultimate) but noticable dmg.
• Very short coolddown - 20/16/12. Really that what makes her pain in the ***. Plus the next point...
• If you hit enemy with Q before using Lunar Rush then there is no CD - you can use it again! WOW! So try always to use Q on enemy carry before fight - this way you will be able to finish him when he starts to run away. In 1v1 situation you MUST hit enemy with Q first 1) to do more dmg (you will be able to hit R twice) 2) in case enemy will want to escape you close the distance with ability to jump on him with second R).
• Don't use it to be first in teamfight - you will be CC'ed and annihilated.
• In critical situation you can use it as escape tool - just R to far away minion.
• This skill unfortunately doesn't proc on hit effects.
  

This is how R skills looks:

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This is the range of R skill (same as Q):

You want to adapt your skill order according to what type of enemy you have top:

1) Is he melee or ranged:

• For ranged enemy ( Vladimir, Kennen. etc.) you max Crescent Strike first - you take them with 2-3 hits to half HP and then finish them. If not - it will just be poke fest.
• For melee - depends on play style (see point 2)

2) If he is passive or aggressive

• If you play vs defensive player like ( Nasus, Shen, etc.) - max Crescent Strike first to poke him and don't let him even dream on attacking you.
• If enemy champ plays aggressive ( Riven, Udyr, etc.)- max Pale Cascade to at least level 3 before maxing Crescent Strike to defend yourself

More squishy = more dmg, so you have to find YOUR balance. To do that you may consider:
1) At what elo you play - if you are below 1400 you can go glass cannon build easily ( rylais as 1 tanky item will be more than enough)
2) How you doing in lane phase (to get advantage ask your jungler to help you or you can take Teleport and port to bot when enemy jungler surprises you bot teammates. You can fed from this a lot)
3) How much risk you wanna take - more risk, less defense, more AP, more FUN :)
4) How good you are - I know you are the best but...it may be your bad day or something :)
5) How bad your enemy is - if they kill, gank and rape your team maybe it's good idea to get little defensive items.
6) How many times you played Diana - maybe its good idea to play defensive few first time to see how things work with her.
You need some time to judge some of those things and change your build accordingly.

You can play Diana top 2 different ways:

1) BURST (Top and Mid)

Most people will play her as burst AP champion - and they are correct. Her skills composition makes her best assassin at the moment - her target is to harras from distance and when the right time comes - jump on enemy carry and make him 0 HP in 2 seconds. And she can make that without any trouble, but to do this she needs to maximize her AP:

Final build I try to achive:
rylais
+item of your choice: / /
.Description:

• - you need them to improve early dmg, to get those early kills
• rylais - HP + AP + slow - what not to like. In this first "big" item you get nice package of everything you need to get those first kills: 1) you get AP (dmg) 2) you get HP (defense) 3) you get slow to increase your killing ability. I replaced Rod of Ages/ Haunting Guise with Rylai's Crystal Scepter in my core build (RoA - too much time to build, HG - didn't do much).
• - thanks to rather low cooldwons Diana profits from this item a lot. This is your most important item. You can't imagine how much dmg you do with this item on Diana before you try it! Just remember to AutoAttack after using your every skill. This Lich Bane gives you also magic resist to help you survive the moment when you go inside a teamfight (never first!) to burst your E, W. Additional run speed is also great for chasing nearly dead victims :) It also gives you mana for those long fights to not let ANYONE escape. In build order I tested to go the Lich Bane before Rylai's Crystal Scepter but you didn't have enought survivability - you need Rylai's Crystal Scepter first.
• - time for really big guns. If you thought Lich Bane gave you win in this game treat the Rabadon's Deathcap as a FATALITY!
• - you have to have it - you are AP dmg dealer. Enemy team will have some magic resist so this item is ALWAYS a must!

And 1 last item you have to choose depending on enemy team and how you are doing - you put it somewhere inside build (the later the better - try to stick to core build order above):

• - buy it in really long games or if enemy team is really tanky. Other case to buy it is when you feel that they focus you really hard. Which will be in almost every game - in most of the time this item is my personal choice as a last item.
• - when there is some AP mofo in enemy team who thinks he can be better than you. Especially good in mid lane - currently (20.08.2012) taken by mid AP top players as first item. It helps also in a teamfights to minimize dmg from random AoE (AreaOfEffect) skills.
• - Use it enemy team has lot of AD damage or you feel that they easily burst you. Very good item in AP burst playstyle. After someone initiate teamfight and after that you go Q,R,E, W you find yourself inside the battle without any escape abilities. You could Flash out but with you can put some chaos to enemy team plan. At the moment they realize you are reachable they focus you, but when you activate skill they don't know what to do - some will wait till it pass, some will switch to other target - but you will get moment of consternation. And this can give you and your team time to win this battle. It really works amazingly.

Why not:

• - takes too much time/money to build and make it kick
• - it doesn't give you any AP. You are AP carry, burst damage should be your thing, not attack speed, not building MR with every aytoAttack.
• - no matter what you are AP champ - you will get more dmg from Lich Bane

2) HYBRID (aka. test/fun-troll build)

This is where the fun begins - you can build her as AP but with AS (attackSpeed) items to proc her passive. Her passive is not "minor", "not important" like for example on Ziggs - it really makes a lot of dmg, it's scaling with your level+AP and you can try to make your playstyle out of this. You can make whole build around this passive. It would be big pity if you do not use it.
Downside of this is that you need attack speed - so you have to give up some AP (not so big burst anymore) but if you make 3 items: rylais you will have fun from playing Diana like with no other champion. Hybrid build gives you possiblility to do dmg even when all your skills are on CD (CoolDown).

Final build I try to achive:
rylais

.Description:

• - hit, hit, hit - PROC. You need AS (attackSpeed) from any source you can get it keeping high AP
• rylais - you need 1 defensive item in this build. It gives HP,AP and slow for every skill you fire. Great item!
• - for additional slow, heal and dmg.
• - What? Are you mad? This items is usless ****, you NOOB! OK - have you tried it on Diana? Try it and write in comment how you liked it. In this hybrid build you need AP and AS - this item has both. Plus it also gives you tons of CDR and mana regen. There aren't many other items giving AP AND AS at the same time. Besides it's my build - I use what I want. For me it works - BIG TIME! :)
• - slow + spell vamp + life steal + AP + AD. Tested on JAX and Akali many times. You heal with it, you easily chase with it, you do lot of damage with it. Great item for this build.
• - time for big guns
• - if you got here it means it's game over (for enemy team)

Consider instead of last 2 items ( , ):

• - if enemy stacked a lot of MR (magicResists)
• - treat it as luxury item when your doing well and you have time/money to buy it instead of pure dmg. It helps in long battles and thanks to that item you can surprise enemy champs with your sustain. Your shield skill + this spell vamp makes magic happend (and enemy rage)
• - when there is some AP mofo in enemy team who thinks he can be better than you. It helps also to minimalize dmg from random AoE (AreaOfEffect) skills.

Why not:

• - takes too much time/money to build and make it kick
• - it doesn't give you any AP (for 2 most important skills for passive and your Q)
• - no matter what you are AP champ - you will get more dmg from Lich Bane
• - seems like good defensive item (armor + immortality active) but above hybrid build is meant to be solo/godmode/pumbstomper so if you need to use that active than it means you need someone to help you when you are in active mode. It shouldn't happend - you must avoid those situations. Also you don't have any channeling skill during which you could use this active. This item is not so usefull on Diana.

Items: Boots, 3x Health Potion

This is most important point in entire game. You can easily die! Just like that. Why? Cause all your skills do AoE (AreaOfEffect) dmg - so you push no matter what you do and enemy team will catch you out of balance:

• Last hit with Q - you push.
• Enemy attacks you, you use W - you push.
• You AA (autoAttack) - every third attack makes AoE (AreaOfEffect) slash - you push

But you have to last hit somehow - so you push and enemy jungler will realize this very fast.
You need Doran's Ring, Doran's Ring (and a sight ward if you play top lane) as soon as possible to even think about fighting your enemy and for defending from ganks.
Additionally think here about Akali - every enemy team (smart or not) will realize they have to shut down you early or you will be their nightmare late game. So they WILL focus you!
So what can you do?

• Call your enemy jungler for lvl 2-4 gank. He can help you to get a kill. He can prevent enemy jungler ganks. If you get a kill - you won your lane.
• Call for sight ward from your jungler.
• Try to force enemy to push himself - some enemy champs will have AoE (AreaOfEffect) skills too - stay close/inside your minions - this way when they attack you than they attack your minions - so they push plus 1) your minions attack enemy champ - it hurts in few first levels 2) your minions stop attacking enemy minions but enemy minions still attack them - so in the end enemy push, you not (you dont risk gank from jungler).
• Get Boots as a frist item - you have bigger chance to escape. Worst case scenario - you dont have Boots (you took Doran's Ring), but both - enemy champ and his jungler have Boots. So they catch you with ease.

In general - easiest strategy is that at start you buy Boots and get fast gold (focus on perfect farming) for 2x Doran's Ring and sight ward. Place sight ward correctly: 1) Mid lane - best know spot for me is in enemy jungle, on path from river to "between Red and Wrights", 2) Top lane - usual - somewhere on a river. Now you can push how you want. You will see enemy jungler coming and thx to Boots you will be able to run in time.
Next steps depend on enemy you face - check "Lane matchup" section for detail. But in short now you will search for kills :)

Items: Boots / Doran's Ring / Doran's Ring / Blasting Wand

Here I describe situation you will meet in ranked games below 1400 elo, where everyone thinks all other players (enemy but also your team) are n00bs. And they play terribly bad. If you are in elo hell like me you know what I mean. And Diana seems like good champion to get out of it :)
So your main target now is to kill your lane enemy. Sounds easy, harder to do? Not true! In current patch having 2x Doran's Ring Diana can kill most enemies easily by this simple plan: poke enemy till he is less then ~70% HP with and then go all in with combo: / / / / / . Sure kill. I couldn't believe it before I tried :) You can compare this burst damage only to LeBlanc and Akali damage. But it's easier to land, has longer range and you are more tanky than those to ladies. Killing machine.
After first kill farm a little more to have >860 gold and go buy Blasting Wand and 3 pots. Take blue buff.
Now every time enemy comes back you do same combo and kill him even more easily. You have better items (more damage) and higher level.
So you think you gave all you can to win this game? Sorry - not true. Now it's the harder part - you have to win all other lanes, because they are for sure failing. First check which of 2 other lanes is doing better and go gank there (push your lane first, kill you lane opponent if possible):

• Ganking mid/top lane - ping your teammate to let him know your coming, write him to start fight and jump on enemy when you see he went "all in" vs your teammate. Thanks to Lunar Rush you will be able to get there fast to support your teammate and even if he was losing he shouldn't die so you get kill + assist.
• Ganking bot lane - tell your teammates to push hard to enemy tower. Go and wait in bush between their tower and blue buff. When enemy turrets start hitting your minions ping map to let your AD carry and Support to let them know you start gank. All together, with 3 people you should be able to kill both enemies before turret do. They usually don't suspect that they will be dived under turret, and don't suspect attack from back. For this one you can also call your jungler for help - it makes this gank easier to perform, with lee risk of anyone dying.

  Best way to gank bot lane:

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  If bot don't want to push:

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  If bot isn't warded:

If you managed to help your team to win at least 1 other lane you should win the match.
Now continue ganking, steal buffs, call team for dragon.
All above will not only give you gold lead - it will give you morale advantage. And morale wins games more often than gold/items advantage. First they will call a noob mid lane player who was killed by you. After that they will call a feeder player which you ganked... Deaths, no buffs, no dragon, no vision, no map control - they will lose teamspirit, they lose will to fight, they lose hope... All they will think about is to give up on 20 min mark.
Good Job!

In short:
/ / / / AutoAttack / / AutoAttack / .

In long:
When a teamfight starts (in order):
1) hit on some squishy enemy carry,
2) hit to him (inside of battle),
3) hit to pull everyone around closer to you and immediately
4) hit - shield procs (BUM,BUM,BUM - it makes LOL amount of damange at the moment),
5) AutoAttack (to proc Lich Bane),
6) now they start to run,
7) hit and start AutoAttack.

If anyone survived (hehe...) and he was touched by your last you ] to him and start rape with AutoAttacks. Remember always that AutoAttack procs you passive and after every use of any skill they proc Lich Bane - so remember to always AutoAttack whenever you you skills on CooldDown.

After you pull (E) some enemys in the middle of teamfight and hit your shield (W) you have to be careful - did you and your team made enough damage to make enemy team start running away? If no and they jumped on you use Flash, or it's the best time (after you pulled some enmys in 1 place) for you teammate to hit AoE ultimate (like Gragas - Explosive Cask, or Annie - Summon: Tibbers, etc.) - it's easy for them to perfectly land it + it allows you to escape from middle of fight and start you combo again from safe position.

Remember also that most of enemy champs are slowed from you Hextech Gunblade / rylais so you will have a lot of time to dmg with you AutoAttacks.

I will put here some advices I can think about regarding matchup against certain champions I played against as Diana.
Also I will put in brackets level of difficulty of that matchup (range 1-10, 1 easiest, 10 hardest). I got this from "goldfather8" Riven guide (best one I saw).
I will add more champs when I make few games against given champs.

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Jax (Difficulty - 9)

Lane:Top
Skill Sequence:
Starting item: , 5x

Man Jax is tough champ. Whenever you try last hit he hits you back like a truck with his Empower. Whenever you get close to him he jumps on you with his Leap Strike, stuns with Counter Strike+ and hits crazy dmg Empower. After lvl6 his Ultimate makes him hit harder + gives him MR (magicResists).
To sum all above - you don't want this matchup! Swapping lanes with someone is best option here. He will not let you last hit, he will even zone you, with correct movement he will dodge your Q or force you to push lane (standing in the middle of minions while you hit him with Q).
So what CAN I DO?
Tips:

• First thing is to start with , 5x - it will let you last longer
• Go 9 pointes in defensive Masteries tree - Hardiness , Durability and Veteran's Scars are you friends here - more defese, more HP.
• Max your Pale Cascade first - to absorb some of his damage
• Do not kill minions with if you will push (it's possible to kill single minions with it but it's hard) - otherwise Jax + his jungler will eat ya!

OK - now you can survive - you are tanky. You will be able to survive to lvl6 and maybe try to win your lane with help of your jungler. But that's not the point of Diana to be tanky - you will not do much damage with such skill sequence and tanky item build.
As I said - swapping lane with somone is best idea for you for now. I will try to think something to make it better when I play some more games against Jax top in future.

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Kennen (Difficulty - 5)

Lane: Top, Mid
Skill Sequence:
Starting item: , 3x

Pretty standard matchup. Theoretically Kennen is more mobile than other AP opponents, but vs Diana it doesn't help him a lot. He can stun you, he can hit you with his ultimate, but it doesn't do much damage vs our somehow naturally tanky Diana. Keep him below 50% hp till level 6 to not give him stupid idea to call jungler and try to kill you. Poke him, at level 6 kill him. Simple.
Tips:

• If he buys Boots as first item it's harder to hit him with Q, but he is more squishy - so when you hit him it will hurt a lot. So make him suffer :)
• If he buys Doran's Shield he will be able to survive more damage but it will be easier for you to hit him. Again - keep him low HP all the time.
• Move back a little if he puts first "Mark of storm" at you to not give him a chance to stun you.

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Nasus (Difficulty - 2)

Lane: Top
Skill Sequence:
Starting item:

The biggest problem in this matchup is...no not Nasus. His jungler. Nasus don't push at all, he want to be leaved in peace to farm his Q. In 1v1 fight you do what you want with him. But every time you push, every time Nasus will be low - jungler will come and beat ya.
Tips:

• Buy ward FAST even if you have to leave nasus farm, and miss some CS (good point is to take Teleport as a summoner skill)
• When pushed too far push him to his turret and go gank mid
• If you feel safe (warded/you see enemy jungler somewhere else on map like bot) - duel Nasus - force him back to town or even kill. He can't compete with you

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Mordekaiser (Difficulty - 5)

Lane: Top, Mid
Skill Sequence:
Starting item: , 3x

He will hit you and your minions to generate his shield - he will push. Try to stay away to avoid any damage - he doesn't use mana - he can poke you till the end of time - but you don't have so much HP (and time hehe...). You can't go last hit so finish minions with your . In this matchup you don't have to worry about pushing too much - he will push harder. He will try gather money for Hextech Revolver, but you will go back faster for 2x Doran's Ring + sight ward. When you are back from town you can be lucky - Morde didn't go buy yet - he will be still in lane. Poke him 2 times with and go all in > > > > . If you manage to kill him you get lane dominance - do the same thing every time he comes back (ward against enemy jungler). If he killed you - you can try to kill him one more time but you have to poke him more before going all in. If he killed you again - you are screwed hehe... - don't try him without help of your teammates anymore (call jungler etc).
Tips:

• Poke him with your Q when new minions wave comes, just before he hits your minions with his E to generate his shield. This way you lower his true HP, not just shield. It's very important at lower levels, when he doesn't have spell vamp items yet, so he can't get back his life.

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I will add Top Lane matchups as soon as I play with Diana against more top lane champs.
The biggest question at the moment is - how much will she be nerfed. You don't think she will not be nerfed :) But I think like for most champs (for example Irelia) nerfs doesn't do much - champs are good thanks to type of skill it has not the damage it does - this rule concerns mainly assassins.

Thanks for reading my guide - hope You liked it. If yes/no - leave a comment why yes/no (if you have time).

Best Regards,
SteveJoobs