Ap Ezreal is already good. He doesn't have a lot of wave clear, or any cc, sure. But he makes up for it in massive poke, burst, and of course a global ult he can use for execution and team fights.
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Is my typical Early to Mid game path. CDR Ezreal is pretty underrated. When you consider his Q already reduces cool downs by 1 second on all other abilities when they hit an enemy/monster, it makes for a very interesting play style.
Morello's keeps your Mana up pretty well. Lich Bane procs on almost literally every Q, which will already do around 300 Damage, + an additional 400 AP Damage, making it a hybrid move. Not to mention all the AP you'll build late game. And if the enemy is stupid enough to not build MR, allowing you to splurge on a
instead of a
Then you're doing even more damage on ridiculously low cool downs.
CDR Ezreal also has a wait time of 36 seconds on his ult - How many Q's you can land. In other worlds. Ult before a team fight, land a few q's, and your ult is typically back up as the team fight has begun to end.
If you ask me, Ezreal as a Mage is already pretty viable. If they increased the range on his W a little it would certainly help him out more, but he's not in a particularly bad spot.