My eye test tells me that Jimmy Butler is currently the best man to man defender on the team. I don't know about help defense and I haven't looked at advanced stats, but again my eyes tell me he is already the best man to man defender on the team.
As far as everyone being so concerned about a 2nd shot creator, while I empathize with your concerns, whatever happened to good ol' fashion ball movement and unselfish play? We have one of the best scorers in the league (Rose) whose job is also to set up his teammates. On top of that, all of the players on this squad are good passers. Noah and Boozer in particular are great passers for being bigs. We also have an elite coach who will/should design the best offensive sets, and I expect Rose to continue to improve as a player maker.
But can we at least all agree that Butler at the 2 is far better than Keith Bogans and the corpse of RIP Hamilton?
EDIT - I think Jimmy's ceiling is prime Ron Artest (without the crazy)