To be honest, Veigar feels even more toxic to play against than before the changes. Before I could bully him out of lane and had a clear window of "beat this guy now and win". Now, sure I can dodge the stun, but why does that even matter anymore? He can farm from behind his turret and I can't even resort to body blocking the skillshot because it hits twice. Riot swapped out "no counterplay insta-stun" (which actually had plenty of counterplay) for "I can't do anything to stop him farming anymore" (which is really bad). I'm not the greatest player, but I can certainly tell that he is more broken than he used to be. Not more OP or less OP, just less healthy. Before, he scaled from weak early, good mid game, godly late game. Now he is just ok early, better than average mid game, better than average late game. I could care less about dodging the stun if he can 100-0 burst me mid game without W or E (and I know to build hourglass and MR and health into him). He farms AP too easily, but doesn't scale as well as he used to, which kind of just leaves him feeling really bleh to play against. I used to be able to say "yeah, I got outplayed and he made it to late game, WP Veigar." now it is just "yeah, this sucks, I can't deny farm, I can't really bully him, but at least late game he'll only get me down to 10% instead of all dead". If I get behind now, I can catch up to Veigar. SERIOUSLY? Veigar shouldn't be getting ahead unless I misplay or he makes it to mid-late game. I shouldn't catch up to him when he is ahead either, because he is supposed to scale harder than anyone except maybe Poppy or Nasus (but the way they nerfed his ratios, I actually do now). This leaves him feeling icky to play against like his power curve is more of a power scribble than anything.
TL;DR: Veigar's scaling is out of whack right now, his early game is too hard to shut down, but he doesn't scale hard enough late game either. It isn't just "less extreme" scaling, it is counterintuitive and un-fun to play against.
EDIT: It certainly feels like he only has three abilities right now though, lots of Q spam, R whenever it is available, E for zoning and an occasional stun if I get body blocked by minions or another champion, and W is a total non factor. Last game I played against Veigar, he 100-0ed me several times during mid game, but he only landed his W maybe one of those times.
Basically, what makes Veigar unfun to play against isn't that he can stun instantly or that he can burst, it is that if he does stun me, I'm helpless and the game gets spun in a 180 from me being up 2 kills and 15 CS to dying 6 times in a row while hugging turret. He is feast or famine. He has plenty of counterplay, and had plenty before, but the same issue stands: if he lands stun, you can't do a single frickin' thing. The nerf to E only made it so that Veigar famines more than he feasts, without actually solving anything, because if he feasts, he is still just as toxic and anti-fun as ever, and if he famines he is just as anti-fun to play as. They need to address how binary his kit is, but all they did was make it more binary.