I think a lot of his critics don't realize or don't want to consider that he isn't a big guy and when he is in aggressive mode he is taking a beating. He paces himself, and imho, he has been wise to do so, most of the time.
I have been irritated with his lackluster efforts too but the bottom line is when he goes all out, he is a top 5-10 player and he simply CAN'T go all out all the time.