It's really uncanny that they'd remove a relatively niche champion's core item, promise to buff them in exchange, and then ruin their entire kit for shits and giggles. I mean, don't get me wrong, Veigar's stun was annoying as all hell with certain champs when handled by someone that could reliably land it on your face, but his kit is so limited that it actually somewhat balanced out, since he'd drop everything on the target and if it didn't get a kill he'd have to waddle away with absolutely nothing left to contribute thanks to his massive cooldowns. Without the stun, the Q is minor poke, the W is never hitting anything except the wave, and the ult isn't going to be enough to secure a kill.
I can conceivably think of one way for this to be redeemed (though it would take a lot of tweaking), and that would be to rework Veigar's AP stacking into something more like Nasus, where he could reliably stack a lot of AP somewhat quickly, either by buffing the Q stacks or by straight up adding AP stacks to his W. Then his nerfed ratios and weaker stun wouldn't matter as much since he'd be getting 400-600 AP per average game from stacks alone anyway. Depending on how things worked out, it could produce some kind of weird ranged AP burst mage tank (RDC, maybe VS, then tank items). Add some built in CDR and you have a brand new, viable late game AP champ that doesn't need to fold to the LeagueofBlinking philosophy in which every champ must have a mobility boost and abilities that make them masters of everything (see: pre-nerf Yasuo, Gnar). Of course, it would be really easy to overtweak and produce a champ capable of melting full build Sion, but it'd be a nice rework of a relatively straightforward and soon to be obsolete champion.
Somewhat on the same topic, I've heard rumours that Kassadin might have his ult range cut down from 750 to 450, or slightly more than a flash. This makes me a bit annoyed, since Kassadin has been crawling back into the meta after beatings from the nerf stick mostly because of the recent item reworks destroying the mana regen of his former pre-6 counters, long ranged lane bullies, while his W lets him sustain and poke forever. His damage is really underwhelming in of itself, his ult only realistically ever has 4 casts, his early game is quite weak (assuming his lane opponent isn't an idiot that walks up to take poke every 7 seconds without returning fire once), and he's only circumstantially useful anyway, mostly against heavier AP teams or squishy teams. Put a Kassadin against a team with two or three AD bruisers and he becomes totally useless. I really don't want one of my favourite champs to end up like Syndra.