Veigar E delay reduced on PBE, but it's still a "stun" that can't stun non-CC'd, non-stupid targets.
The current PBE notes have Veigar's total delay on his stun reduced from 1s (.25s channel, .75s delay) to .75s (.25s channel/delay, .5s pure delay). It's also nice to see that they're planning to make Veigar's cage stop dashes. And, as I've said before, I'm all for changing his E from an edge-stunning mechanic to something more, well, cage-like. His cage is definitely stronger now that people can't dash out of it.
However, I think it's important to emphasize the major shortcoming* of the first round of nerfs, which persists here: his E is a "stun" that cannot actually stun a competent target, unless they're already CC'd. There probably will be lots of Corkis getting stunned trying to Valkyrie out of his cage in the weeks after the revision is sent to Live, because most people won't be aware of the change. Once that effect wears off—and, sure, it might take longer to wear off in lower MMR bands—Corkis will no longer be stunned by the cage. They'll just have to wait inside the cage longer.
The nerfed Event Horizon can definitely zone people out of an area. It can do that better now, with these changes. However, it still cannot actually stun a target, unless they're either already CC'd or else AFK (standing still or pointlessly running into the wall). That's a significant difference. If a target is stunned, Veigar can hit them with his full rotation, and possibly 100–0 them. If a target is not stunned, he can hit with his R, maaaaybe hit with his Q, and almost certainly not hit with his W.
In teamfights, the problem with this new Veigar is that he's really only got one trick: he can throw a stun somewhere to split the enemy team, and he can lob damage into the fray while he does it. There's no more cat-and-mouse game with the enemy squishies; he can no longer either go for that 100-0 or else try to line it up just-so to stun multiple members of the enemy team. He just tosses the stun down and forces the enemy to be somewhat split up for a couple seconds.
In 1v1 situations, the problem is that…well, he's pretty helpless. Previously, 1v1s were high-tension situations in which you got a kill if the target was squishy and you hit your stun first but got killed if you missed the stun or were too slow. Now, Veigar throws his "stun" down, and…then the two of you throw damage at each other. Basically, every stun now works like a "missed" stun with Old Veigar, and turns into a facepunching contest (which he loses). They could buff his numbers to the point where he could win a facepunching contest, but even if he ends up viable that way, I think it'll make him much less interesting.
Put another way: the first round of Veigar nerfs changed his "stun" into a zoning tool. This second round of revisions definitely buffs him, but still leaves him without a stun. I think they either need to come up with some way to make it possible to stun a non-stupid, not-already-CC'd target, or else give his E some new mechanic to replace the stun.
An alternative would be to increase the amount of time the stun walls stay up. That would make it more of a real decision for the Champion stuck inside, as to whether to "break through" the walls (and take a 1.5s-2.5s stun) or stay inside the cage for X seconds until the walls collapse. Right now, it's a pretty subtle tradeoff, and it's not generally going to be worthwhile to eat the ~2s stun (depending on level) to avoid 3s of zoning. Even if it lasted for 5s, as long as Anivia's wall, it seems pretty obvious that in a 1v1 you just stand there and kill Veigar from inside his cage, rather than stunning yourself.
*: Possible short joke.