I agree GP needs a nerf, but that's a wrong nerf.
http://na.leagueoflegends.com/en/news/game-updates/patch/patch-617-notes (in case you guys want to look at it)
You're making him just like the old GP with long CD's and terrible early game. Here's what you should do: Remove that extra gold earned from his Q ability.
This is what GP does now when he's nerfed. He either plays safe until he gets his first item (farm with his Q with the extra gold) or Barrel (E) you down while still playing passive. Why are you nerfing GP's W and R ability? Stop putting long CD on those abilities.