mostly historically sub has scaled well. simcraft showed it origionally but now its shying away from that. Im honestly thinking we will see sub becoming viable around T16 (in ICC it was viable, in firelands-DS it was viable)
to hayturr: it depends on what youre attempting to do. im in a high end progression guild, so im going to play the spec that is the most effective at doing my job, which is 99% of the time, doing more dps. if im not as good at playing sub, yet sub is the best dps spec for that fight ill work my butt off to become better at sub (had to do it before). if youre in more of a casual guild, or just looking to have fun, by all means, play what you want. it is a game after all. if the question is "top dps spec" then mut is the answer (and combat in certain fights). because you dont enjoy mutilate dosnt mean it isnt a higher dps spec than sub.