The only thing that I think he needs a rework for is how annoying he is. Seriously, why are there champions that only exist to be a pain in the ass? I can understand one champion whose sole purpose is to be a royal pain in the dick, but league has far too many.
I know it requires some setup, but in a 1v1 situation, he can suppress you and you are forced for about 2--3 seconds to watch yourself die. It's one of the most excruciating things in this game to watch. I know, to get a full 100-0, he's got to put his DoT on you, put down his aoe, and a voidling would help your chances of a kill in just one ultimate, but when he does it, it is more frustrating than teemo shrooms. Yeah, you can complain about how he never really runs out of mana, but that's pretty much anyone with Athene's Unholy Grail and a doran's ring. But, the fact that one of his skills is so hated, so annoying, so cancerous, that they call it "Space AIDs?" I think this mechanic makes the game less enjoyable, imo, and there are way too many champions with mechanics that make the game less fun to play as it is.
I'm conflicted; on one hand, he's pretty balanced because he takes some skill to get his combos and picks in lane. But I also have the last paragraph that I ranted about his anti-fun mechanics, so it's a pretty hard sell, to get riot to nerf/rework him. If you could just point out that a champion is "anti-fun" and persuade riot to fix it, Yorick, Teemo, Malzahar, and several others would have been reworked a long time ago, and people probably wouldn't complain about them as much.