Have fun landing any CC when you get poked to death for coming in vision range. I've done about 30 blind pick games on Proving Grounds, and from what I've seen poke teams almost always win against other comps.
What people don't realize is that Proving Grounds isn't like team fights on Summoner's Rift. You start at level 3, and one poke can take a third of your health away. Poke teams build up such a huge gold and level advantage that other comps don't have a chance.