I love Viktor, I think his skills are right on.... Wouldn't mind if his shield had a tiny bit more defensive strength early game.... But skill wise, he's set.
Only thing I've noticed that warrants a change is his special staff item. Most people consider his recommended laser buff "right" and both others "wrong." I've had some pretty good results with the speed buff granted by his shield version.... But the stun version... I don't see any reason people would pick that.... Which is why I've never seen anyone try it outside of the times I've tried to make it work.... The increased range effect just doesn't help that much.... Yea, you can stun farther away, but now they're outside of your range to affect them while they're stunned.
Even the stats on it are fine... But I suggest changing the effect. I think people may consider buying the stunstaff in some games if it significantly boosted the size of his field rather than the range. Keep in mind, it's not instant, so any characters that can jump (agri, Wu Kong, fizz, Rivan, lee sin, shen, jarvan, etc. .... About half the league) ... Plus anyone with flash are essentially immune to it unless they're silly. Boosting it's size so it's not SO easy to flash out of would definitely make people have to think whether they want a more reliable stun than moar burns.
That is all.