Why was Veigar stripped of his identity?
Riot decided to buff up Veigar's scaling passive in 6.9, but in doing so they had to completely remove his identity as an anti-mage. For the first time ever, Veigar is countered by glass cannon mages like Ahri, and nothing has really been added to help him against ad assassins in mid lane.
His ult does less damage now unless you trigger it when the enemy is at almost 0 health, and he no longer has any scaling on the enemy AP. Veigar used to be a mid laner pick to counter squishy mages, now he's just another squishy mage with not mobility. Where's the benefit of this? The only improvement is that he gets slightly more mini-game in hitting enemy champions as well as minions.