Veigar was getting a little out of control before his rework that took place prior to 6.9, forget when it was, but he wasn't getting a ton of play. They then changed his q to a skill shot and made his event horizon delay and he went back down a tad bit, though at higher elo's he did a bit better if I remember right due to him being able to farm 2 minions with q if the wave is set up right, compared to the previous 1 point and click.
What was holding him back however was first the little assassin meta mid we had for a time and then right before this patch what was holding him back was that games were snowballing so fast he never got to his lategame potential.
With the change in 6.9 veigar is able to achieve more of this lategame potential earlier and he is becoming a problem again even with the short lasting games. Not to mention if a game reaches true late game now he is even more ridiculous than before.
Annie on the other had has always been busted and from what I've seen that hasn't really changed.