Orianna Build Guide by Noitcurtsed
Not Updated For Current Season
Not Updated For Current Season
Note: All the opinions of this guide are based on playing on Orianna's strengths as bottom lane, rather than a solo. Many champions have many builds and this guide's suggestions are based around this role Orianna can play.
One of the newer champions riot has to offer, Orianna the Clockwork Girl, plays unlike any other. Her difficulty bar is full for an obvious reason: The Ball. Most champions use abilities from their current location, but not Orianna. All of her skills (save for Summoner Spells and auto attacks) are centered around The Ball. This causes the Summoner to have to essentially control two objects at the same time.
I view Orianna as a walking HP bar. I keep her safe from harm by staying on the side lines while The Ball does the dirty work. This way you are the last surviver of most team fights and can often go a match with less than 4 deaths, despite not building any HP or defensive items immediately.
If you follow this build and guide, you won't have enemies curse you in All chat. In fact, they may not even know you were there. See this as a strength. Orianna can turn the tides of any fight while being unseen by enemies. This means they wouldn't think to run...
Pros / Cons
Great AoE Burst
Very good at farming
Insane range by use of The Ball
Great field control
Can zone enemies extremely well
Ultimate is synergistic with many other champions ultimates (Nunu, Amumu, Jarvan, Pantheon, etc)
Command: Protect make's fighters into tanks and tanks into gods
Good at initiating or supporting an initiator
Can lane decently verses multiple opposing champions (2v1, 3v1)
Mana intensive early game
Slow base movement speed
Damage limited by cooldowns (9 seconds on main damage skill)
Low single target burst compared to other mages
Limited by The Ball's movement and placement
Predictable because of The Ball
On Orianna, I feel that Flash is a near necessity. One great aspect of Orianna is that once you have a gap between you and a enemy champion that is chasing you, they will not catch you (Exception: Phantom Dancer stacking Yi). Your W, Command: Dissonance, will allow you to not only speed yourself up, but it will slow champions chasing you. And when you get jumped, the best thing to create distance is Flash.
Going true support style with this pick. You may think it looses viability since The Ball can be used as a ward itself, but the power of CV is much more than that. Setting up ganks, preventing ganks, and giving vision for long skill shots including your own. I have killed many enemy champions through walls, inside our jungle, and at their towers because of CV. Choose it in one game, and wonder why its good. Choose it in 20 games, and then you can never live without it.
I don't see Teleport as a staple, but it has many uses and I prefer it when another CV exists. It allows you to farm a lot more, protect towers, and counter acts her slow movement returning to the battle field. And since you will be farming with her, you need to take an item/blue trip several times in a match. Teleport helps get you back in the fight that much quicker.
Other viable options:
Ignite will help fill a hole in Orianna's attack scheme and get you some early game kills. It becomes a better choice when it will hard counter some champions (Soraka, Dr. Mundo). One disadvantage is its extremely short range. If you want to make full use of ignite, you need to build some early game survivability like RoA or stacking Dorian's Rings. Because of this, Ignite is not suggested in this guide and left for solo Orianna.
Cleanse will make Orianna that more survivable. Like stated with Flash, all you need to do with her is create some distance. If you get stunned, feared, or anything, escape is a quick Cleanse + Flash away.
The main advantage that Exhaust would give is it would allow for you to use The Ball without much prediction. Exhaust + Command: Attack + Command: Shockwave + Command: Dissonance will make for a quick gank.
Many other Orianna player's swear by Ghost's usefulness. I agree to a point, because Orianna is very squishy and can be ganked very easily. For what Ghost provided me, I felt a different summoner spell would fill a hole that Command: Dissonance couldn't fill. I know, Ghost+W means NO ONE can touch you, but the times in which Dissonance wasn't enough usually meant either I made a mistake or someone was fed.
This choice of masteries is pretty standard for a mage. Orianna's range allows her to not worry about defense as much and go for a 9/0/21 build. You would want to obviously switch out Spacial Accuracy and Blink of an Eye for your respective Summoner spells.
I know that many other's say this talent is avoided in many builds, however I felt as if Good Hands was wasted on a champion that died an average of 1-3 times a match. Since after you build Archangel's, you have around 60 mana per 5 seconds, an extra 4% would be 2.4 more mana per 5. This is close to Meditation, so it's good enough for a tier one mastery for me.
On Orianna, I do not get this mastery because I don't feel that Orianna gets enough benefit from it to warrant the points MID/LATE GAME. Blue buff would cap out you on cooldown reduction sooner (or without runes), but I do not like relying on a temporary neutral monster buff for a major stat such as cooldown. If you're building it because its a crucial stat, I feel you shouldn't rely on something that could be stolen from you. Mana becomes a non-issue later in the game so that aspect of Blue buff isn't needed either.
Red buff would be good early game, but not as good as it could be for other champions. It is not advised to get Red buff on Orianna, unless you solo que'd a team of all AP users.
TL;DR Because you build an early Tear of the Goddess and Fiendish Codex and can cap CRD with just an Elixir of Brilliance there is no reason to have blue buff mid/late game. Give it to your AP carry. Red buff is not advised
Presence of the Master and Sorcery
These are taken to get as close to the 40% cooldown reduction cap as possible before any in game items. Using these allows you to make full use of all of Orianna's skills, while making up for her low AP ratio's by stacking nearly exclusive AP.
This mastery adds more to Orianna's much needed Magic Penetration. Because her skill's don't hit as hard as most mage's, a focus on Magic Penetration is necessary for maximum damage. This is explained further in the Items section.
Magic Penetration is usually the best choice for all AP users for maximum damage, especially early game. Orianna is no exception. In fact, it could be argued that Orianna needs more Magic Pen than the average champion due to her lower AP ratios.
For Seals, I chose to off set her low mana regeneration pre-Archangel's with mana per 5 second per level seals. They become equivalent to flat mp5 seals at level 6. 1-6 is boring and slow as you ramp up your tear, so I see no reason to not have these.
Flat cooldown reduction glyphs, along with Quints and Masteries, allow Orianna to reach max cooldown reduction at a very low level. This is extremely useful for Orianna, since low cooldowns mean more of your amazing ultimate and more shields for your team.
These top Orianna off as going able to get max cooldown reduction just after purchasing Morello's Evil Tomb. The only disadvantage: Not taking Flat HP Quints makes you VERY squishy early game.
I also like movement quints here. They offer extra field control in addition to her dissonance. Because Orianna is innately slow, the movement speed allows you to kite much more effectively. For this however, I feel is better for building an AP carry solo Orianna which this guide is not.
Last hitting minions
Early game (1-10) Harassment
In the mage/support role, her passive does very little outside early game. You should not forget it however; because of it your auto attacks hit especially hard straight out of the gate. Orianna's attack range is shorter than most AD range carries and mages (550 units), so keep that in mind.
Positioning The Ball
Early Game Harass
Command: Attack will be the first skill point you get. Why? Because otherwise, Orianna will not be able to move The Ball. And since all attacks (minus auto attacking) come from The Ball, it is best to have control of it. Proper use of this skill will require practice and a lot of it. The Ball moves slow. More often than not you will need to predict enemy champion movement with this skill in order to land a W.
There are many fun tricks you can do with this skill. These are gone over in greater detail in the "The Ball" section
The attack severely reduces damage as it hits creep. 10% each hit to a minimum of 40% damage. Stack that on top of a low AP ratio (60%) and this becomes a spell almost used exclusively for positioning. Because of this, it stays level 1 until late game.
Despite it being level one, early game with skill offers some excellent harass. Especially if your opposing lane does not have heals (Janna comes to mind). It only costs 40 Mana on Rank 1 with a CD of ~5s. This means with your Meki Pendent, Runes, and Masteries you'll only use ~20 Mana every 5s is you use this on cooldown. Throw the ball in their back lines and move it back and forth for free harass.
Escaping a fight
Chasing down champions
This is your bread and butter skill. Its a swiss army knife of abilities. It slows enemies, speeds allies, and does good damage all in a small AoE radius around the ball. The movement increase/decrease gets better as you level it and it does more base damage than your Q. It is MUCH easier to hit than your Q as well. (Note: There is a bit of delay in the time you can activate Dissonance after positioning with Attack. This takes some getting used to, but is not game changing)
All of this makes Dissonance your first maxed skill. It starts to pack a real punch after getting it to Rank 3 and you obtain your Sorcerer's Shoes. I would advise you to wait until level 5 to really start opening up the harassment with Dissonance because of this. It's mana cost is a bit heavy before you charge your Tear fully, so be wary of spamming it too much.
Having a walking Command: Attack
This skill is the main reason I consider Orianna a support in addition to a mage. This is the reason Orianna can be built with very little HP and Defense and still only die in VERY extreme situations. I max this skill second in this build because its increased shield and resistance/armor is worth much more than damage on Attack.
It is important to note that as soon as you pick this skill up, Orianna simply holding The Ball will give herself the MR and AR buff! This adds a lot to your early game survivability.
If you get a Rabadon's Deathcap after Morello's, your shield will be a ~600 HP shield every 5.5s that is a clicked ability with 925 range. For reference, Morgana's shield has 600 range, Jana's 800, and Lux's 1000. So Orianna's shield, in my opinion, is the easiest and most practical in use due it its superior range and being a click ability verses Lux's skill shot. For more note's on how amazing this shield is, please see the "Support or Mage?" section.
Another monstrous advantage of this shield is that when it is on another champion, The Ball is moving with him! No need to Command: Attack for positioning anymore, throw that shield on a melee and use him to damage enemies. This is where Orianna's range comes in. While your Q and E have 925 range, you can be a whole 1124 units from The Ball and continue to damage enemies. You can literally be out of the site of enemies and still be great support for your team. Your shield should ALWAYS be on someone. This build offers enough mana and regen to do so. Your shield should ALWAYS be on cooldown in team fights.
Initiating Team Fights
Escaping a fight
Interrupt (Eg. Kat's ultimate)
Many, many, many more...
This ultimate is probably one of my favorite to use. Not visually (I give that to Blitzcrank), but mechanically. It does the most damage out of all of your skills and is definitely the hardest skill to use effectively. Not only is there a slight activation delay after you hit R, but the radius is not that large.
In practice, Shockwave pulls all enemy champions a fixed distance toward The Ball. This usually nets in movement closer to The Ball, but it is possible to be moved away if the enemy is on top of The Ball already. Orianna is no exception to that you want to level your ultimate whenever it is available to do so. More uses of this ultimate are listed in the "Support or Mage?" section.
For starting items, with the mana mastery in the utility tree along with the mana regen from runes and Meki Pendent you can easily sustain your mana in lane until you can build a few items. Health Potion and Mana Potion help by allowing for more aggressive early play. Dorian's items are amazing solo, but for bottom lane potions will take you further.
Tear of the Goddess is built as soon as possible. This ensures you will reach maximum mana fast. After it is built and charged, mana becomes a non-issue. You will need items before taking a blue trip if you play conservatively and buy a few Mana Potions in the early game. This means not missing or overusing Dissonance.
Your next trip back defiantly needs to be boots. Orianna moves so slowly that she needs the extra speed. This will prevent ganks when your is used. Only buy the prereq boots however, you need to build up your mana pool first. You will defiantly want to continue to buy a few potions (mostly mana) until level 9-11. This will give you time to build your mana pool and regen and use pots to make up the difference. I usually try to buy two or three of each depending on where my gold situation is and how hard I am pushing/they are pushing.
A note on wards: You really need to have around 2-3 on you at all times. When pushing lanes with your team and over extending in general, it saves lives.
The fact that Orianna can get away with 1-2 deaths per match makes a Mejai's Soulstealer an early game item choice. I love soulstealer on duo lane Orianna. Because you get Tear and max CDR first, the soulstealer give you extreme levels of AP in comparison to your sustain and spam. Orianna is amazing at kiting and running. Her field control and sustainability keeps you alive in impossible situations. Stacking soulstealer is easy if you are a proficient Orianna player.
Just remeber that not every game should have a soulstealer in it. If your mid is feeding LeBlanc, DO NOT BUILD IT. Use your judgement. Sometimes building some defense quick at this point is advisable. However, if your lane got first blood do not hesitate to build this.
After the tear, finish your boots with Sorcerer's Shoes. This will maximize your early game magic penetration. This is crucial for Orianna due to her low AP ratios. Because you are focusing on support over mage, you will have low AP until mid/late game. And because you won't be seeing big numbers on your Dissonance and Shockwave, minimizing the % reduction from resistance has huge impacts on your staying power early game.
A lot of other guides (and the recommended items) suggest building Ionian Boots of Lucidity instead. The reason I avoid them is two fold. Magic penetration is decently difficult to come by and Orianna really does need it to allow her to do respectable damage. The Sorc boots offer an easy, cheap way to obtain Magic Pen very early game.
The other reason comes from wanting to achieve maximum cooldown reduction fast. I explored different options to do this. One is to use and instead of the flat ones. This would allow you to cap with just the boots. The problem with this is that is assuming you are level 18. The /level runes for cooldown become equivalent to the flat at level 13. This guide can max cooldown before that point easily, so I felt this was a superior option.
Mercury's Treads are another viable option. Though, again, the magic penetration is too useful in my opinion. The Tenacity gained from the boots will increase your survivability greatly however. Considering your low HP and little defense, Orianna is very susceptible to CC. If you are finding you have problems with CC and don't want to use Clarity, then give up the magic penetration for these.
Codex is built next to provide with early game CDR. The main purpose of building this before Morello's is to cap out on CDR (39.8%) by purchasing a Elixir of Brilliance. This allows for maximum harass and support with the level of sustain you have with Tear of the Goddess
I love Aegis on Orianna and build it early over Rod of Ageas. Not only does this item net you 30 Armor, 39 Magic resistance, and 290 Health, but it also allows your Command: Protect to give a total of 42 armor and 45 magic resistance to any ally instantly.
I much prefer this over RoA because armor and resistance stack so well with her shield verses getting the nice health boost from RoA. Plus this item's cost is SIGNIFICANTLY less than RoA (1925 gold compared to 3035). After getting your Soulstealer, this defensive item goes a long way for you and your team.
Morello's Evil Tome comes next. It is important to note that with the runes and masteries in this guide, this item will give max cooldown reduction (you will be at 39.8%) at this point in the game. This means after ~7,000 gold, you will achieve this plateau of shielding, support, and nuking speed without any neutral buffs or elixir.
At this point, the game play style should be more towards team fights. Now that you have a good mana pool and you can spam your abilities, it is best to rush Archangel's Staff next. For only ~1800 gold, it will net you ~104 AP, 18 mana per 5, and 50 extra mana. This will set your mana regen at the point to need to be to fully utilize the cooldown reduction you just achieved, while adding a much needed chunk of AP to your arsenal.
This is the point in the item build where you have to feel out the game. Are you needed for more of a damage role? Are the opponents stacking lots of MR items? Are you dieing a lot due to anti carries or pro assassins? You basically want to chose between buying some defensive items, building a Void staff/Abyssal Scepter to counteract stacking MR, or continue stacking AP.
NOTE: I want to emphasize the importance of build prerequisite items and molding your character to the situation of the game you're in. If I know I am going to build a Banshee's Veil because of a fed Karthas, build Negatron Cloak early. Maybe even before Morello's Evil Tome.
Banshee's Veil is a great item on Orianna. Stack this ability on top of your shield and high mobility means you never being caught in a bad situation. If there was an Annie or Fiddlesticks running a muck in the game, I would pick this up after building Morello's. Adapting to the game you're in is a huge part of becoming a good player. While you can get away with very little defense on Orianna, this strategy sometimes backfires and you need to adapt accordingly.
Are a few of the enemy champions stacking magic resistance? You can choose between Void Staff or Abyssal Scepter to counter act this. With the way magic penetration works, in order for the -40% reduction to be worth it, the opposing champions must have more than 90 magic resistance (This is based off of having all nine , Archaic Knowledge, and ).
Keep in mind that this only makes the items break even in penetration and only for those characters with 90 or higher resistance, otherwise it is less. Also bare in mind that the Abyssal Scepter supports your team more as well and has magic resistance on it to boot.
Nearly all champions only have 30 magic resistance without either using some MR runes or masteries. And since you have around 30 magic penetration with your boots, unless the opposing team is building magic resist, skip these.
Zhonya's Hourglass is a unquie and extremely powerful defensive AP item. It adds a nice chunk of AP and allows for a free oh **** button. At this point in the game the enemies should be gunning for you anyway and with Hourglass, you have a free ~3 seconds where they can't even target you. This allows your team to focus and peel champions off of you. I would get this item if they had a Nocturne, Master Yi, or Tryndamere that was doing well.
Will of the Ancient's would be a good addition if you have a lot of AP users in your group. Also, I have experimented with Lich bane a few times. It adds very nice damage at this point, but I personally don't like getting within 550 units of death.
Deathcap cleans up the build with a huge chunk of end game AP to push your support and damage over the edge. If you don't need any defense outside Aegis of the Legion, Death Cap sends you over the edge in damage and shield power. By this time, your skills are taking chunk's of HP off of carries. You can be decently aggressive now and your Q+W can knock out an entire minion wave very quickly.
So to sum it all up:
, OR ,
Support or Mage?
Since riot posted Orianna on the main site not listing her as support, there has been a split to which category she lies in. I believe Orianna is a mage/support. More offensive than say a Zilean, but not near the support of a Soraka. Why do I emphasize her support qualities?
Her shield and MR/AR buff
Her Command: Protect has two simultaneous uses: It shields AND boosts defense. This makes this skill extremely potent in making any champion much more durable than they normally are. Many other's feel that it doesn't (And her abilities in general) scale well with AP. I want to address this:
Her E may not give a huge amount of armor and resistance and the shield may not be as large as Janna's, but the difference is that it simultaneously shields and increases the effective HP of your target, which also makes the shield more effective. For notes on effective HP, please see Mathematical Explanation of Stats (including EHP) created by Larias. If the shield scaled any better with AP (currently its 60%), it would be grossly OP.
The correct use of this shield will set good Orianna's from bad. It allows Orianna to be decently aggressive while having little defensive items. It also can make a team member into a tank. Not every champion, but certain ones. For example, I often play with an Udyr. At one point I had full cooldown reduction and over 400 AP from a maxed Mejal's Soulstealer. Because of this, Udyr was able to tank the ENTIRE opposing team with taking ZERO damage due to the defense he had and Turtle Stance by me recasting Command: Protect on cooldown.
You will save champions with that shield. I at least save 4-5 early/mid game kills on my team mates each game. This is the nature of Orianna.
W is an AoE slow and speed up
This is one of the big roles you will play in team fights. You control the speed of both players on the field. I cannot tell you how many more kills I got for my team with Command: Dissonance. Nothing helps chase down a runner down more than slowing them while simultaneously speeding your melee and tanks up. The true essence of a support. The speed boost does help Orianna, but once you reach your opponent you will have a hard time stopping them unless you have Exhaust. Aiming Command: Attack at a runner is difficult, though it can be done successfully.
Another huge use of your W is running. When a team fight goes sour, no one is better at getting the entire team to safety than Orianna. Simply all of you running together and a quick Command: Dissonance will speed up everyone while severely hindering the opposing team's chase. Even if they avoid the AoE of your W, they need to run around it which slows them down anyway.
An AoE Pull-in
Note: I said pull in, not knock back. Her ultimate pulls every opposing champion in the AoE radius a fixed distance toward The Ball. This can sometimes end up netting movement over and away from the ball for champions already close, but more often it pulls them closer to it.
I love her ultimate. It has uses only limited by your imagination and it truly supports your team. Initiating team fights is easy when every enemy champion is tossed and disoriented for a second or more. As stated in the pros and cons section, her ultimate also synergizes with many, many other Champions. One notable use that I actually performed in game was help Jarvon catch three champions in his Cataclysm. Needless to say that was a triple kill. I also have wiped out an entire team's tower push with a sole Pantheon by combining his Grand Skyfall with my ultimate, hitting all five champions in the center for maximum damage. Cleaning up was easy after that.
Low AP ratio's and little on demand burst
These two go hand in hand with describing her level of damage compared to her support ability. My conclusion: Her damage can't compare to pure mages. I am not sure if this was the intention of riot, but unless you are severely fed you won't be getting that many kills.
Her Q scales with 60% of your AP
Her W scales with 50% of your AP
Her R scales with 70% of your AP
This means you're going to need a lot of AP to take those champions down. And since every time you Commmand: Attack you reposition The Ball and risk loosing field control and make it harder to set up a W or E for your team, most of the time your Q will be used solely to predict a runner's movement and slow with W. And this make's the damage portion of the skill less useful.
Don't misunderstand; if you use all your skills in tandem you put out good damage. Your Command: Shockwave has a relatively low cool down, but not low enough to use multiple times in a team fight. Because her burst is so reliant on the consecutive use of all her skills, and the ultimate is much better used to initiate, pull runners, or to combo with other champions, her burst lacks.
Know your role
At the beginning of the game, you have to make a choice. Solo or lane? In my opinion, Orianna in the early stages of the game is one of the better solo characters. Her duo laning ability is very good also, but it is heavily reliant on having a good partner that also knows Orianna well. Despite the fact that if you build Orianna for it, she is among on the of best solo lane champions in the game due to her superior range, harass, and CC this guide is focusing on the duo lane Orianna situation.
Because of her low HP (especially if you follow this guide and skip ), not every lane partner suits Orianna. It is very easy for two champions to CC you and kill you using the brush to get the jump. Because of this, your partner needs to understand how Orianna works and when to add his/her harass on top of your own. Remember to use The Ball to check brush. This can save your life.
So you're in a duo lane and you want to pick a laning partner? Orianna excells at harassment at range and this guide meshes well with a champion that would only take selective damage and benefit from your slow/speed up greatly. Since you level Command: Dissonance first, it would be best to have your partner either be a ranged carry (AP or AD) or a fighter (Tanky DPS/AP).
I have had great success with all of the above, but I think Orianna+Assassin ( Poppy, Akali) is just wrong. Loosing first blood will be the least of your opposing champion's worries.
Examples of great champions to lane with Orianna:
Poppy Akali Wukong Pantheon Nocturne Kennen Annie Brand
These levels are slow. Only focus on last hitting minions and use The Ball as more of a mental harassment than one that will hurt their HP. If you use low rank Dissonance (ranks 1,2) too often, you will leave yourself open to ganks, being pushed, and not be able to push a kill/recall so you can roam and help your lane mates. Play conservatively and smart at these levels. I don't even use rank 1 Dissonance unless they try and jump me. Remember to harass with auto attacks and Command: Attack. Clockwork Windup is most useful at this stage.
Now is when you can really start putting out damage. Once you get your Command: Shockwave, ganking and killing becomes a lot easier. You should still be buying HP/MP pots at this stage to make up for your low MP pool until your Tear of the Goddess becomes maxed. Most champions feel safe at their tower, but not anymore. Pull them away from their tower with your ultimate to get those kills. Orianna is great at support for ganks. Your slow/speed boost on top of the shield and ultimate to pull runners is extremely effective at getting your carries double kills. Roam and call out where ganks are comming.
Team fights are in full swing at this stage. Your shield is now rank 4/5 and it is time to make good use of it. The longer team fights last, the more chance you will have to win with an Orianna at your side. This is because this guide boosts unlimited mana and max cooldown. The shielding, supporting AoE damage, and speeding/slowing put out by her allows any team fight to dramatically shift with the addition of Orianna. Ultimate them and they will scatter. Slow them, chase them down. Shield your teammates. But most of all: STAY ALIVE! Remember, your W and R have a 1124 range! Throw Command: Protect on a tank/fighter and start popping the damage. I have saved small team fights without the opposing champions even noticing my presence.
The Ball is the reason that Orianna is such a challenge to play. The Ball has many uses and if you want to unlock Oriann's true potential you need to know the tricks.
The top is the range of both her Command: Attack and Command: Protect. Decently large right? That's 925 units of range which is very far in this game. Even at this range, not many champions can't hurt you ( Sivir comes to mind).
If they could barely get close at 925, the end of The Ball's range will be impossible for them. This is the second image. As you can see, its almost at the limits of your screen. This allows you to do many fun tricks with The Ball as will be explained in this section.
These two images are the reason why I don't care to build defense. If only a handful of champions can hit you with 1 or 2 abilities, if you play smart you won't be touched.
Much more to come...
Questions and Answers
You didn't take any gold per second items. Why?
Orianna is just amazing at farming. All her abilities are AoE and once you get used to them killing waves of minions and getting lots of gold is easy.
Why no Rylai's Crystal Scepter?
I see this item in the recommended items and in a lot of other Orianna builds. I feel that this item's slow offers very little to your normal play style. It adds a slow to your Q, E, and R. Protect will not be used for damage that much and Q and R are usually followed by Command: Dissonance directly after casting them anyway. A big use would be that you could aim your Command: Attack at runners and slow them, but why not just do this with Dissonance and pick up a more powerful AP item instead? This item is almost as expensive as a Rabadon's Deathcap and you only get 80 AP.
Why no Rod of Ages?
I really like Rod of Ages on a lot of characters. It offers everything a AP user needs while giving you a nice MP/HP boost each level. However, I feel that building Archangel's Staff and RoA is overkill. And because choosing RoA over Archangel's nets you 630 HP, while loosing ~50 AP, 775 mana, and 25 mana per 5 seconds, I don't feel RoA is a good alternative for this build. The HP just isn't needed when you will be so far back in team fights and your escape ability is amazing. It would especially hurt to loose all that mana regen.
Who is Orianna's ideal tank?
The tank that I have loved time and time again protecting my Orianna is Alistar. His CC in tandem with your own is enough to make your opponents rip their hair out. I actually have had teams curse ours in All chat for the level of CC there was with our Annie, Alistar, and Orianna. Combine that with Alistar's ability to peel melee carries off of your squishy support mage makes him the optimal choice.