I feel PBE Veigar can be good, he just needs some touching up
W and R are probably fine as they are
Q could use an increase to the AP gained on unit kill (1--> 2?; 5- -> 10 on champion kill), mathematically even with perfect CS, current PBE Q just barely gets you back to pre-DFG live veigar values, given that most people won't be getting perfect CS (if anyone will really) it definitely needs an improvement.
E is the bigger issue, it needs (and I cannot stress needs enough) some kind of reliability improvement, whether that happens in the form of an AoE slow within the walls of the cage, or a decrease in the delay before the walls appear; is up to riot, but it needs something of that nature.