I recently watched Curse.NA defeat AL at the ggClassic. In my opinion it was Nyjacky playing Veigar who really made the difference. Once he got to "nuke status" with his DFG and just enough AP he was able to burst down from 100% to 0% any single champ on the other team, or damn near close. The game changed dramatically once Veigar was at his full his full potential as before this it was actually pretty close.
So why don't we see more Veigar play? I know that there are some hard counters to him both in lane and in end-game situations, but I still don't know why for example he couldn't be saved for last pick. Especially for teams like Curse who have such a dominant player like Nyjacky.
Here are some stats from elobuff.com
As you can see Veigar is in the bottom half of played AP champions and is 69th overall amongst all champions.