As a season 2 & 3 Veigar main, I like Veigar's changes. BUT...
Like I said, I believe Veigar's changes are healthy and going in a good direction. Just because movement creep has become the IN thing doesn't mean he should have an unfair insta-stun so he can 100-0 people with almost no punishment (other than he loses his one shot and his disengage, becoming near useless for the rest of the fight). I think Riot is going in the right direction with Veigar, this change makes him an overall healthy champion that is maybe even LCS worthy.
Or it would IF... Using Veigar's E actually felt like trapping a person. Swain has his snare, Viktor has his slow/stun field, and Orianna has her ult. After a delay like the one implemented, there should actually be some sort of pay-off. Right now, especially with so many dashes, an enemy can flash, blink, or just dash through the E and get the stun; even just waiting it out in there and dodging the W is good enough. Anything they do can screw Veigar over, because they aren't actually trapped, they just have to not walk into the walls and avoid his W (and maybe now his Q) which isn't too hard given the time it takes to come down and the limited AOE. Going close to the enemy can actually make you the fucked one, because once your Wall goes down, it is free game for them to tear you a new asshole. Think of his E currently as putting an insanely dangerous prisoner inside of a prison cell with electrified walls that will crumble in a few seconds and you only have one shot to properly put that prisoner down before he gets out. All that prisoner has to do is not touch the walls, dodge the bullet, then jump on you and tear your throat out for getting too close to a crumbling prison cell. Overall, it may be more dangerous for you to approach them if they didn't walk into the .75 second to erect stun walls than it is worth. If you can't hit them with your W and go in to try and burst them to only fail, then you have no more escapes and they have free reign to just put their throbbing champion wee wees into your cute purple bumhole.
So, because there is no point in just saying what is wrong with it, I will give some suggestions to actually make the enemy feel "trapped" inside of his E, like Riot described how they wanted an enemy to feel if Veigar could hit his E successfully.
A. Make it so that enemies put inside the box cannot dash out of it, like with Azir's ult's wall.
B. Slow the enemies trapped inside by a small amount and keep them slowed for a small amount of time once they leave the wall/the walls fall (whichever comes first; with the slow scaling down over 1.5 seconds).
C. Allow his W to increase splash radius to fit inside the entire box if used inside his E, but keeping it so the splash doesn't exit his E so it doesn't allow him to hit his W even if the enemy escaped before the walls came up.
Those are just some suggestions. If you agree with my message, like the suggestions, or even just want Riot to get to see a response about Veigar that includes constructive criticism/feedback to hopefully get them to continue looking at this champion instead of just letting him gather dust after their most recent changes to him, please upvote this post. Commenting also helps and I would love to hear your responses or read the discussions sparked by the thread.