Diamond+ opinion: Don't nerf Veigar W, nerf his Q + R.
Don't nerf the only thing that takes somewhat skill on Veigar.
Nerf his Q: travel speed too fast/damage too high. Nerf his R: ridicoules damage, especially vs AP champions. Remove the enemy AP scaling or reduce it significantly to 30% enemy AP scaling. Or Keep the scaling, but make it a skillshot.
Let him have strong W, nerf his Q and R.