His mains problems IMHO are :
-1 Non interactivity. He has only one spell to interact with his ennemies (E). That's a super mega bad design and a big failure from his rework. Yeah, he has his passive that can deal tons of damage when it adds up. I don't care, anyone can aa in this game, most get more rewards for that since he's immobile and melee.
-2 Low impact skills (bar ultimate) with next to no scaling (every single one of them, a little less noticeable for the stun, especially noticeable for the heal). But that coud be fine : they're low impact because they're supposed to be spam-chained permanently (high cd higly reduced when weaved) to make him impossible to defeat in a sustained brawl. This is why he has high cds on all of his skills : because he's supposed to chain them, not rely on one maxed ability and keep the two others for utility / emergency purpose. I'm fine with that. But they fucked that up by limiting him with super high mana costs that drain him in no time.
I don't care how overpowered his ult can be, it's so full of counterplay (burst faster than 2,5 sec, disengage, cc them during the ult, or just scare them...) he deserves better than that. Right now his ult makes me think of the ohmwrecker active.