Well it has to do a lot with swing changes, unless your Bubba Watson these golfers need repetition and consistancy. Especially with Tiger who is a workaholic. When you work on your swing, and make a change, he needs hours upon hours to make that comfortable He's rewriting all those hours he has done before. So there's that, and he's getting better we can see that. Three wins this year is nothing to scoff at.
He is feeling the pressure, he cares to much of what people think of him, no matter what he might tell the media. You can tell because he gets pissed at the media. You can see he tried to fix when he said he tried to play relaxed. Then he goes on, that was a bad idea you know how i am, i am pretty intense guy. So basically his intensity is not working, so he threw that out and tried to play relaxed and it blew up in his face. He doesn't know were to go and he doesn't know why he's messing up. I still think he is rusty on his short game and putting, and he has an issue with left to right winds because he can't cut the ball consistantly, and he ends up pulling it left.
Basically, his game is not sharp at all. Its because he keeps messing with it, and since its not sharp its messing with his mind. He's a thinker to, he takes in everything, he will back away from the shot if the wind changes 1 mph, somehow he knows :p. This gets him into trouble, because the wheels in the head start turning and all of sudden he gone, his mind has totally clogged up the game. When he was good, it was because he KNEW that his swing was there, he KNEW what the ball was going to do, he didn't have uncertainty. He has uncertainty, and its showing.
to fix this, he really needs to stop tinkering with the long game. Accept it at a place he can be at, maybe its not perfect, but he needs to accept some level of completeness in his swing. Then he can go on to the short game and putting and give that attention. Once he's able to have acceptance of his swing, and gain some sort of stability, he'll win more majors. Until then he might have to get lucky to win one, like Rory throwing away the master's a few years ago. Because there are to many guys who can put 4 rounds in the 60's in majors. Its not just Tiger anymore, there's always 1-2 guys who can be there on sunday.