Ezreal Build Guide by Xunn
Not Updated For Current Season
This guide has not yet been updated for the current season. Please keep this in mind while reading. You can see the most recently updated guides on the browse guides page.
AP/Magic Pen !
Build 1 - The Happy Ending
Build 2 - CDr ASAP but lower damage
Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
EMERGENCY TOOL [aka OMG I JUST PICKED EZREAL 'COZ HE'S FREE TO PLAY!NOW?]
How many times we all did something similar!? Ahahah!
Well, all you have to do to start is scroll back at the top of the guide and click on the third face of Ezreal you see on your left. You will read "SKIRMISHER PLAYSTYLE": set masteries/runes/summoner spells like showed and go for the itemization showed in the BUILD 1 BALANCED END - MY BUILD.
Don't solo, go TOP with your teammates.
Harass enemies as much as possible and try to be present in every teamfight, play safe and overextend only if you're sure to get the kill. Keep your ulti to stop enemies from capping towers.
Don't killsteal. Don't afk. Don't flame.
Now you're a pro and a real man. Go in peace and have fun with my blessing. <3
Introducing This Strange Player And His Strange Guide...
Hi all, I am Xunn from Italy, and I play League of Legend since January 2012.
I've always loved Moba games, and I started with DotA many years ago (around 2003 maybe, I'm not sure...). In DotA I did some tournaments under the nickname of Lightbane, then I gave up moba competitive play and started play other games.
I've discovered LoL in january 2012 and started to play it but always avoided ranked games and similar: now I just want to have fun when I return home after work, so I mostly play Normal games with friends (IRL and not) in Crystal Scar, and sometimes also in 3v3 Twisted Treeline and 5v5 Summoner's Rift.
Basically I play AP casters, and my main picks are Brand, Xerath, Gragas and Diana.
This doesn't mean I don't play AD champs at all (I really like tricky ones like Jayce, Jarvan IV, Udyr and Zed ), but surely can give you an idea about why I've planned an AP build for Ezreal when I've seen that's viable. Since then, Ezreal has become one of my main picks. ;)
So, that said, I can't say "OMG, TRY THIS BUILD AND YOU WILL OWN 'COZ I PLAY PRO UBER ELO!"...
I just wanted to share this build I've made up for Ezreal with other people, hoping you can have fun with him as I do!
Always remember that a Guide is just a bunch of suggestions and many words: the skill and the reading of the gameplay should be yours. So, if you think that something here is wrong for your gamestyle or for the match you are about to play, you are OBVIOUSLY encouraged to change what you don't feel comfortable with!!
Last but not least: if you're going to downvote this guide, please take a moment to leave a comment and tell me what you didn't like about it. By doing so, your downvote can be considered like a mature suggestion to improve the guide/change mind about some part of it.
I thank everyone who will find some minute to read this guide, even if he's going to downvote it in the end, because this will balance the time I've spent to write it!
"There's no one with truth in his pockets", after all.
Let's go... and HAVE FUN!
Introducing the Cooldown Reduction Idea...
FIRST OF ALL:
MY USUAL BUILD IS THE FIRST ONE IN THE " SKIRMISHER PLAYSTYLE " BUILD STYLES, the one named BALANCED END 1 - MY BUILD (the third build from the left, up there)
TWO BASIC THINGS TO KNOW BEFORE READING THIS GUIDE:
-CD Reduction (CDr) caps at 40%.
-In Dominion games, 99 times out of 100 you will not get more than 4-5 items. It's really hard that a game will last long enough to get someone the full build.
Well... Many of you maybe are shaking their heads reading about CDr Ezreal, most of all 'cause his low initial damage (expecially his autoattack damage, which gives him almost no chances to stop a minion wave [that is the main reason why you should not play a solo lane])... So... Why play an Ezreal of this type?
Because his ultimate, Trueshot Barrage, is really helpfull in dominion!
As all the all-map-ranged ulties like Karthus/ Draven/ Ashe ones, that skill can be used to prevent people from capping points or for a big harass. Playing with the opportunity to cast it every 48 seconds means that an Ezreal with a good map awareness can prevent almost everytime his enemies from capping points/escape a fight with almost no life.
The support tree guarantees also a good mobility that is really nice in Dominion, and improves your kiting/escaping abilities.
Pros / Cons
-Skills ALWAYS ready
-Good kiting/mobility/poking capability
-Continuos harass across the map
-AA speed steroid for all your party (and you) with Essence Flux
-Almost invincible 1v1 Points' Defender (most of all, TOP tower)
-Funny as hell!!!
-Low damage in early phases
-Your highest damaging skill doesn't hit minions, but only champions ( Essence Flux).
-Requires good aim and timing because all his skills are skillshots
-Requires good map awareness
-Usually doomed when you are fighting against blink-on-target champs like Katarina/ Talon, multiple dashers like Akali/ Fiora and Kassadin with is teleport->silence combo.
-You must play Top Lane for almost all the game to get best results
Screenshots/Collages of my Skirmisher CDr Builds
This is my standard build for Ap Ezreal CDr in Dominion Games.
You can find the build (as already told above) in the third build from the left "SKIRMISHER EZREAL" - Build 1 or Build "Gatling Gun" wich I'm using lately with good results.
You will notice the Hextech Sweeper is unamovable from my inventory's 5th slot (and Wooglet's Witchcap from my 2nd slot): this is due to my mouse bindings.
The usual item purchase order is the one described in the build.
Screenshots are important to prove the effective usefulness of the builds and the credibility of the player who wrote the guides...
NOTE: It's not an excuse but just a fact... In these last months, my internet connection sucks really hard. For some strange reasons, I get disconnected often and I can get 30secs/1min of crazy latency dancing from 70 (never had less than 70 ^^') to 2500. I am not joking. Consider that I die at least 1 time/game for this stupid reason. So don't get discouraged if you see that I die sometimes, because it was surely avoidable with a better connection.[/color]
Some End Game Collages...
End Game screenshots:
Whole recounts of a game: (yeah, I am trying the italian client xD)
MAKE PLACEMENTS COUNT !
Doesn't matter what champion you are playing: do your best to help your team!
These pictures are not here to proove neither my force nor anything similar. They are just supposed to be a statement of the influence of an Ezreal in a game when he's played with the right awareness and presence. When people will tell you "Don't Ez pls" "Ez in Dominion? You troll?" just ignore them, lock him and claim top.
If you will play correctly, they will change their mind!
AD Ezreals vs. AP Ezreal...
And remember... YOU HAVE TO LOSE WITH HONOR!
This is an AP build guide, so we will focus on Essence Flux [W], that is the highest damaging ability for an AP Ezreal. This means we are going to take a point in that skill everytime we'll be able to!
The choice about the secondary skill is up to you.
I personally prefer Arcane Shift [E], because it allows you to escape/kite and also LAST HIT escaping enemy champions (it's damage scales nicely with AP and I've took lots of kills with that skill).
On the other hand, Mystic Shot [Q] applies On Hit Effects, gives you an higher farming capability and reduces the CD of ALL your abilities... And everytime you take a point in that skill, his base CD is also reduced (6/5.5/5/4.5/4). That sounds very good... Until you get focused and your Arcane Shift is in cooldown!
So, take a look to the situation before choosing the skill you prefer to upgrade!
Trueshot Barrage [R] is our ultimate ability and obviously must be selected everytime we can to get the best results in game!
So, imho the Skill Sequence must be:
[R] Trueshot Barrage > [W] Essence Flux > [E] Arcane Shift > [Q] Mystic Shot
But no one can stop you to try this:
[R] Trueshot Barrage > [W] Essence Flux > [Q] Mystic Shot > [E] Arcane Shift
For the last build on the right, AP AA EZREAL, you can also dare trying [R] > [Q] > [E] > [W] (I feel bad only to write it in an AP guide xD), or, if you have no respect for your own life, you can dare the extreme choice: [R] > [Q] > [W] > [E]
I don't encourage you to try this unless you are going with an AD Mastery tree/AD runes, but of course you are free to experiment and to let me know...
A stupid Tip (or maybe not?):
-Always try to shoot Essence Flux before Mystic Shot, so Mystic Shot can reduce immediately Essence Flux's CD.
Let's start with Flash: I love this spell and I find it really helpful in repositioning/escaping, so I don't wanna play without it, even if lots of people say that it's useless in Dominion. That's my guide, and that's my style. <3
The other choice in Dominion imho is Ghost, but for CDr Ezreal I've noticed that Revive is good too... Because you can resurrect in a crytical moment and shoot your Arcane Barrage across the map killing unexpected enemies / denying them from capping the point you were previously defending when they killed you thinking "The bastard is dead, let's cap asap!". Aha, who's your daddy now?!
Honestly, Revive has an infinite cooldown that sometimes discourages me from telling others to try with that spell. If you feel comfortable with Ghost, stick with it! In the last month I've always played with Ghost and I feel ok.
Barrier and Cleanse can be viable too... But... You probably will be dead before you can take advantage of them ... Try it and make your idea about this fact. Maybe you have a better connection / reflexes than me and you can do good tricks with them. <3
Just keep in mind that Support Tree doesn't buff Ghost, so you'll need to make some mastery changes to my tree if you aren't going for Revive and Flash!
It is ALMOST IMPOSSIBLE to go OOM in a Dominion game! Manaregen is high and you can find around Health Packs who also grant mana/energy/rage back. So... NO.
Are you serious?
Nice spell, but I don't think it's Ezreal problem to bother selecting it.
Nice spell too. I've seen some people using it nicely... But I think that Garrison is more for a tank champion who plans on defending his team's points, or for someone who frequently dives. Your skillshots has enough range to keep you out of truble while harassing defending players. ;)
I don't think that is something worthy to be taken in consideration in Dominion.
The Crystal Scar's aura reduces self healing too... Why bother about Heal when there are lots of Health Pack all around?
Hard point this one...
I see people loving this spell. I don't. Or, at least, not enough to take it with me in the Crystal Scar. Obviously Ignite has a nice diminishing heal (anyone thinkin about Master Yi channeling his heal while the towers keep attacking him with no results and you don't have a thing to stop his channel?!?) and the DoT can kill an enraged Tryndamere at the end of his ultimate... The choice is yours. I still don't like this spell.
Nothing worth the disturb.
Never liked this spell except rare situations.
Masteries are basically all focused in the Support Tree, with the main target of getting:
-Movement Speed (via Wanderer / Nimble )
-Maximum of CDr [/color](via Intelligence / Sorcery ).
The only exceptions are the Mastery Trees of the builds named MAX DAMAGE and AP AA EZREAL who take the deep AP DPS tree.
Notice that almost all of the Mastery Trees are slightly different from each other, based on giving some more personality and presence to your gameplay as you feel more comfortable!(For example, see the points in Artificer when the build includes Deathfire Grasp/ Wooglet's Witchcap, in order to use these items as more as possible.)
Because Mobafire for strange reasons keeps messing up my mastery trees, I've decided to rewrite here the masteries for every build, so you can watch here and be sure the masteries you are using are correct:
CDR ASAP BUILD
FROST POWER BUILD
SKIRMISHER PLAYSTYLE BUILD
MAX DAMAGE/MAX DAMAGE [CDR capped via items]
AP AA EZREAL
( under construction )
BEST RUNESET FOR AP CASTER/POKE EZREAL:
Glyph of Magic Resist 9
Seal of Armor 9
Mark of Magic Penetration 9
Quintessence of Ability Power 3
The main runeset. Great defensive power (Ezreal is squishy) with the touch of initial damage/magic penetration via Marks and Quintessences.
RUNESET FOR AA AP EZREAL:
Glyph of Magic Resist 9
Seal of Armor 9
Mark of Hybrid Penetration 9
Quintessence of Ability Power 3
The runeset for AA AP Ezreal build. The marks are obviously used to improve both the damage sources of Ezreal.
VIABLE STANDARD AP MAGE RUNESET:
Glyph of Scaling Ability Power 9
Seal of Armor 9
Mark of Magic Penetration 9
Quintessence of Ability Power 3
You can go for this runeset if you wants to play Ezreal like a full mage. Remeber this is the best choice to improve damage but it's a lot easier to die. As always, the choice is up to you!
Note: In Normal games (Summoner's Rift) I use Greater Seal of Mana Regen but in Dominion I find them useless, so you can stick with Armor. Other Seals sounds useless to my eyes...
FARMING?!? ARE YOU SERIOUS?!
You CAN'T farm minion waves with these AP/Cdr builds, at least until you'll have a Iceborn Gauntlet// Lich Bane// Guinsoo's Rageblade.
Your main sources of gold will be Kills/Assists throughout the whole game..
In order to help you a little, there is the point in Pickpocket ...
Not so impressive but it is worth some extra gold and it's more rewarding than Greed :P
The choice of Pickpocket is pretty easy to explain: it gives you 3 golds every time you hit an enemy champion with a basic attack (3 because you're ranged). The Cd of this ability is 5 seconds.
This means that if you can aa an enemy multiple times, you can get 3g on the first hit, then other 3 on the first attack after 5 seconds are passed, and so on... This means that you can have a maximum yeld of 3 x 12 = 36 g/minute despite your attack speed, assuming that someone is so stupid to let you autoattack him for a whole minute. (Even if Ezreal's AA damage is pretty low with these builds, we can estimate that 1 minute AA will kill an enemy champion... I hope :D )
The other Mastery, Greed , with 4 points ( 4 ! ! ! ) grants you 2 g/10s, this means 2 x 6 = 12 g/minute. No match!!!
Items  - Items with CDr aka our core
Ok, so what are your best choices when you're ready to spend the money you earned?
[Always keep in mind ALL the builds I'm submitting in this guide tend to the max Cdr]
Here's a list of the top AP/CDr items for my builds:
Morellonomicon: This can be one of your best friends. Cheap, 75 AP , manaregen, 20% CD REDUCTION and healing reduction. 2200 g price
Blackfire Torch: 20% CD REDUCTION, huge damage with AP/passive ability/Magic Penetration. Unluckly, it's not cheap at all... ^^' Consider this item only if you are doing really good and earning many golds. In any case, it's the best CDr//Damage item you can have in your inventory! 3950 g price
Deathfire Grasp: 10% CD REDUCTION and 120 AP !!!! ...plus the huge burst from the active ability! Perfect item for burst damage...if you got fast fingers! ;) 3100 g price
HEXTECH SWEEPER: My favorite CDr item!!! 10% CD REDUCTION, some AP and a nice pair of skills (active and passive) to help you and your team in many situations! 1435 g price
Iceborn Gauntlet: Slow to build cause the medium-high cost, it gives you 10% CD REDUCTION, more (attack and spell) damage (but not competitive with Lich Bane's one), kiting capabilities and (whohohoh!) FARMING CAPABILITY! 3250g price
Ionian Boots of Lucidity: Perfect item to reach the CDr cap asap but you will be going to lose Magic Penetration. Choice is up to yours! 15% CD REDUCTION. ;)
A little note about these boots: That 5% CDr is also complicated to administer, because every item with CDr in the game gives 10 or 20, this means that you will be forced to take 2 points in Intelligence and 1 in Sorcery if you are willing to cap your CDr. Otherwise, you will get from 35% to 45% CDr when at full build. That means you will not cap CDr or you will OVERcap it (basically WASTING some useful stat to get something you can't use...). 700g price
Nashor's Tooth: Very nice item with 65 AP, 50 As and 20% CD REDUCTION. It can be yours with "only" 2500g price. This items gives you 25 flat AP more than Guinsoo's Rageblade (it's also 100g cheaper than Guinsoo) and only 10 AP less than Morellonomicon, with the same CDr (even if Morellonomicon costs 300g less). I love Nashor's Tooth, but honestly I think it's worthy to be bought only in an AA/AP build (that's why I use it only in the last build AP AA EZREAL).
That said, here are the items sorted by price:
Ionian Boots of Lucidity - 700g
HEXTECH SWEEPER - 1435g
Morellonomicon - 2200g
Nashor's Tooth - 2600g
Deathfire Grasp - 3100g
Iceborn Gauntlet - 3250g
Blackfire Torch - 3950g
Items sorted by CDr contribution:
Blackfire Torch - Morellonomicon - Nashor's Tooth 20% CDr
Ionian Boots of Lucidity 15% CDr
HEXTECH SWEEPER - Deathfire Grasp - Iceborn Gauntlet 10% CDr
Items sorted by AP contribution:
Deathfire Grasp - 120 AP
Blackfire Torch - 80 AP ( + Magic Penetration)
Morellonomicon - 75 AP
Nashor's Tooth - 65 AP
Iceborn Gauntlet - 30 AP
HEXTECH SWEEPER - 25 AP
Ionian Boots of Lucidity - 0 AP
It is clear that I use HEXTECH SWEEPER and Morellonomicon in my usual build because they are the cheaper way to cap CDr, in the perfect "CDr cap ASAP" spirit. Dominion is a fast game mode and you have to be competitive asap. The more you can kill/interrupt tower caps in the early phases, the faster the game ends with your victory. Otherwise the HP stacking champions will soon be too hard for you to handle.
In the long run, Dominion rewards the team with more health pool. And it is easily explanable: if you have tons of hp and you fight under your tower, the only thing you must mind is to interrupt enemies trying to channel to stop tower's attacks. The rest is done, just a matter of time. Ok, not an epic way to achieve victory, but surely it works...
Items  - Classic items for AP champs
Here are the classical items for an AP champion who better fits for Ezreal, but with a little math ;)
Items sorted by FLAT AP contribution:
Wooglet's Witchcap 100 AP
Lich Bane - Rylai's Crystal Scepter 80 AP
Void Staff - Abyssal Scepter 70 AP
Items sorted by costs:
Void Staff 2295g
Abyssal Scepter 2650g
Rylai's Crystal Scepter 2900g
Lich Bane 3000g
Wooglet's Witchcap 3500g
Items sorted by FLAT AP/g ratio:
Void Staff 32.78g/1AP
Wooglet's Witchcap 35g/1AP
Rylai's Crystal Scepter 36.25g/1AP
Lich Bane 37.5g/1AP
Abyssal Scepter 37.85g/1AP
From these valors, we can easily say that Void Staff is our best choice: it is the cheapest, the owner of the best gold-for-AP ratio, and it also gives 35% MP. Definitely my favorite choice uless I'm being constantly focused, in that case the choice is always Wooglet's Witchcap.
NOTE about Wooglet's Witchcap: It's % bonus AP is obviously escluded in my flat AP calculations. If we look at that passive, it's obviously our best choice also for increasing AP, but it's cost is really high and when I play the Skirmisher Ezreal build, I already go for Morellonomicon and Hextech Sweeper to cap CDr. The price to pay is that my AP will be lower than the one of other AP champions in the match. Void Staff gives me less pure AP than Wooglet's one, but the Magic Penetration bonus improves my damage in an unbelievable way, and all for only 2295g, that are pretty easy and faster to get. The normal process after chosing Void Staff is to go for Wooglet's Witchcap. Honestly, I have to admit that I've almost never finished Wooglet's in a game when going with this build, because the game finishes before I can buy it!
Belive me: you will love your Void Staff!!!
Items  - Hybrid items AP/AD
Hard part, this one...
I've created a different chapter for this third type of items because it's really hard to give a good comparison of them with "normal" AP items.
Some of Ezreal's skills scales better with AP, others with AD, two doesn't scale with the both of two but only with one (AP) like our beloved Essence Flux and Arcane Shift. So, how to compare them?
The only option I was able to think was to make some math about the effective damage increase they give to Ezreal's skill damage...
Just a little memo:
- [Q] Scales 1:1 AD, 20% AP
- [W] DOESN'T SCALE AD, 80% AP
- [E] DOESN'T SCALE AD, 75% AP
- [R] Scales 1:1 AD, 90% AP
Here we go with the 3 main "hybrid" items, listed for price:
Guinsoo's Rageblade: 2600g 40 AP, 30 AD (Flat values) -> 72 AP, 30 AD (top stats on procs)
[Q] (30+8)= +38 damage FLAT / (30+14.4)= +44.4 damage (8 charges proc)
[W] +32 damage FLAT / +57.6 damage (8 charges proc)
[E] +30 damage FLAT / +54 damage (8 charges proc)
[R] (30+36)= +66 damage FLAT / (30+64.8)= +94.8 damage (8 charges proc)
Hextech Gunblade: 3400g 65 AP, 45 AD.(+His active scales 40% with your AP)
[Q] (45+13)= +58 damage
[W] +52 damage
[E] +48.75 damage
[R] (45+58.9)= +103.5 damage
Trinity Force: 3843g 30 AD, 30 AP
[Q] (30+6)= +36 damage
[W] +24 damage
[E] +22.5 damage
[R] (30+27)= +57 damage
From these values you can easily understand that Trinity Force is useless twice: first of all 'cause his high price, second because the flat stats it gives are laughable. Surely you have all the other passive bonuses but... Go for Lich Bane then! On the flat stats race, Guinsoo's Rageblade it's better, and the Hextech Gunblade is the best, even if the cost is almost the same of a Wooglet's Witchcap.
For these reasons, I keep considering Guinsoo's Rageblade the best choice you can do (cheapest item of the three and medium yeld in your flat damage stats make it the winner!).
Your work is funny and dynamic: you should harass from behind your friendly lines your enemies, ready to Arcane Shift back to avoid get killed or ahead, into the fight, to finish off an escaping enemy. Obviously, don't use AS to kill steal. ^^'
For this reason and because your skillshots will deal almost no damage to minion waves, you need to play top with your teammates, and not solo bot. THIS IS IMPERATIVE.
A reason more not to play solo with Ap Ezreal is that you need a free line of sight to aim your Mystic Shot. If you can't get rid of minion waves pushing your tower, it's obvious that you will have lots of annoying minions on your way when fighting against the enemies... And you can't ignore the minions too, because their attacks hurt as hell and if you don't kill them, they will neutralize your tower... And if minions neutralize your tower, you lose points and many advantages, the first and most obvious is the huge damage the tower does... And your team will flame you... And you will uselessly try to explain that your skillshots are useless in a Dominion solo bot lane... And you will get sad... And you will play even worst... And you will lose and get angry... And your team will call you NOOB... AH! SEE WHAT YOU DID BY GOING SOLO BOT, YOU SILLY BOY!!! No way to play Ap Ezreal this way!
Stay top with your teammates guys, or... what about Heimerdinger!?
An Ezreal with this build must have as a priority target the dominion over the top tower point. For this reason, leave a teammate to cap the mid tower and get top asap at the beginning of the game.
Your [Q] Mystic Shot and [W] Essence Flux will nicely interrupt your enemies from channel the cap, harassing them continuosly! Stay with your teammates as much as you can, keep harassing, use [E] Arcane Shift to kill people trying to escape behind the bushes searching for an Heath Pack, Flash back to the point if needed and keep shooting your skillshots like if you are a gatling gun!
If you got dashers in your team, such as Fiora/ Akali/ Vayne and your enemies are out of your range, don't hesitate to cast [W] ( Essence Flux) on your mates to help them with buffed attack speed! When the battle will be over and the top point will be secured, always play keeping an eye on the minimap; this will be your main skill: MAP AWARENESS!
Remember: everytime you notice a peril for your top point, go to defend it. An Ezreal with this build can easily defend alone the top tower point against 2-3 enemies thanks to the short cd of his skills. You can Arcane Shift in and out of bushes, escaping enemy attacks and damaging them too, preventing them from cap, while your tower is shooting the ones who dare to dive to kill you! And from the bushes you can almost aim EVERY cap point of the tower with your [Q] ( Mystic Shot), so their life will become pretty hard against you. And remember that Essence Flux doesn't stop at the first target hit: it damages every champion it hits on his path. So, if 2 or more enemies are standing near each other, use Essence Flux to stop the both of them!!!
If you notice that your enemies are bringing a massive minion wave to your point, don't hesitate to shoot your ultimate to kill the minions and hurt the champions. You have Trueshot Barrage every 48 seconds ! ! ![/color]
Throughout the game, always remember that top point is your personal target and your responsability. When it is secured, you can roam across the map with your mates and do whatever you want, but never choose a different location from top tower if it is under attack!!!
Once you'll reach level 6, you will acquire one more role: you will need to control the minimap and instantly shoot your Trueshot Barrage to prevent enemies from cap your towers undefended.
If you notice that an enemy with low health is capping with his mates, always shoot the Barrage aiming him. This will force him to recall (if he survives :D ), giving your allies an easier fight to defend/[re]capture the point!
The Fine Art of Sniping [Tips'n'Tricks]
THE FINE ART OF SNIPING:
WHEN NOT TO SHOOT TRUESHOT BARRAGE:
-When your target is low health and teleporting (unless you are pretty near him, probably he will be full healed and in his base when your Barrage will hit the point where he was. Total waste of your Barrage. Doh!)
-When you are sniping across the whole map to interrupt a tower cap and the enemy has already capped half the tower point. As above, the Barrage will get to them too late.
Remember: best Barrages are shot when your teammates are not around your targets scaring them to interrupt capping and leaving their positions!!! I've failed many Barrages because a mate engaged the enemy before my ulti reached 'em... and it's so frustrating... (even for your mates, because a little wait should have given them an easier fight 'cause of the lower life of the enemy ;) )
WHEN TO THINK ABOUT SHOOTING THE BARRAGE (or not):
-When your enemy is aware of your presence (when he sees you and can dodge your skill). So, use Arcane Barrage in short range fights only if the enemies are stunned/slowed/suppressed or they have a certain unique escape way. If they flash or move, you wasted your main damage source!
-When you are standing on a tower point. Points are always visible on the map. This means your enemies can see you shoot the Trueshot Barrage. A good player can move his visual on you (if you are visible on the minimap) during his cap moments to control if you are casting the Barrage at him across the map! Or, more easily, an enemy can see you and tell his mate via vocal chat/ping to move, saving his life and wasting your masteripiece of an aimed shot. :P
LAST RULE ABOUT TO SHOOT THE BARRAGE WITH PROFIT:
When an enemy is running from you, the more his path is near to 90° with your Trueshot Barrage path, the more easily you will fail! If you can reposition to reduce the angle, via Flash or just movements, try it before to shoot the Barrage. ALWAYS REMEMBER THAT BARRAGE HAS A SHORT CHANNEL BEFORE BEING SHOT, YOU CAN'T MOVE DURING THE CAST (AND YOU CANNOT CANCEL THAT CAST)!!!