I think vodoo doll doesn't need anything.
It's an awesome card, you can grind FG's with it, and you can use it in 9001 different ways, as RootRanger said. What you're proposing would buff one of that options and nerf the rest, or just buff it and imbalance the game (vodoo doll is already balanced)
Oh, BTW, don't lock the topic, every card buff/nerf should be discussed, even though it may not be the best option to buff/nerf, it can be in the near future.