People can make the argument I suppose that bulking up hasn't hurt Tiger, but you can't make the argument that it's made him any better either. In no way is he a better golfer in any phase of the game because he can now lift 350 pounds or whatever it is.
He's completely transformed his body and any time you do that you are opening yourself up to injury. Take a look at what he looked like in the 90's and early 00's compared to now. He looks like a different person a la Barry Bonds. (I am in no way suggesting he's taken anything illegal, I just think he went crazy with his working out). Heck, compare his swing from then to now. now he still has a great swing for the most part but it doesn't look near as natural. Looks like he just muscles the ball out there now to me where he used to get through the impact so naturally.