He was pretty OP on the first release onto PBE. He could kill a tower without creep waves with fog of war in about 30 seconds with a Nashor's Tooth. (He could spawn soldiers over walls and autoattack towers and just spam them). They bugfixed that (i think).
There was also his ability to teleport to enemy dead towers and instantly proc the passive. Which i think got fixed as well. He's going to be really strong though. Champions who are able to create void zones at range with relative safety have proven themselves to be pretty strong (relese Heim, Syndra, Zyra, Orianna, reworked Heimer, Lux, Anivia).
His ability to scale hard with autoattacks will give him some unique scaling not typically found in AP champs that aren't Kayle.
Anyway, i think he has a kit that is going to have various bugs and tricks that can be exploited. However, he's going to be very relient on his numbers. Too much range or damage and he'll be oppressively strong. Too little range and he won't be able to do what he needs to get rolling.
i think playing against him is going to be really obnoxious as well. Pretty much in the same zone as Morde/Malz or a Athenes+Blue Ziggs where there is very little interaction and pretty much you just dodging skill shots and trying to keep creeps off your tower while they have all the fun.
Then he'll get nerfed and be weak.
