Nerf Veigar's STUN
That stun is more effective than most ultimates. It's a 2.5 second AOE stun that lasts 3 seconds on the map. Effectively a 5.5 second CC. Never mind that he has no AP cap (which he should have) and his AP ratios are insane. And worst his stun comes back after 14 seconds if he has no CD reduction, and 8 seconds if he does. So you have a 2 second window against Veigar--or if you dodge his stun a 5 second window. Yeah you can do a lot in 5 seconds, but not if Veigar has a TEAM. Oh wait he does it's a team game!
Get rid of his stun.
I played the original DOTA on Warcraft and I love that hero who had a delayed OP ground attack (the one who summoned the inferno). It was so hard to land it, and she had to channel it. It was so much risk/reward it was fun.
Veigar, has the assistance of a crazy stun, no channelling, and practically no cooldown--not to mention infinite mana and AP.
NERF VEIGAR.
Why? Because he can just drop a stun--his team will take a tower--and after that he will take some kills.
Let him channel something--not drop a spell and run--and let the stun be smaller, easier to get around--or at least stun when inside not when outside. Nerf him. He's an AP Hypercarry.