That's the exact reason he's shit. I mean, you can't do stuff like that and expect to not be gutted in other aspects. He permanently scales his AP, his ultimate just like any other casters ultimate does massive damage, AND does extra based on the enemy's AP. Ofcourse the rest of his kit's gonna be shit with such an overloaded ability.
My point is not that veigar's broken, but his kit revolves too much around just point and click everything to whomever's unlucky enough to get stunned. So in order for the enemies to not feel like shit whenever veigar initiates his point-and-click Q.T.E. he got dumpstered in many aspects.
By the way that R did like, 1800 damage?