@OP: My buddy who was a consular>sage got to lv 30 in beta, got the game and was allowed to keep his character. Though he hasn't been able to play since launch, he told me it was moderately difficult but possible in relatively short time if you just keep at it [if getting to a good level in a timely fashion is what you're after]. He didn't skip very much. Some side missions, but did them for the most part. But that was beta, though...
I'd suggest a ratio of tedious "busy-work" missions to "fun" missions, 5 to 1 or at least 3 to 1--my only qualification being online app games and such where you have daily missions sparring/vs fights, and then the super or special missions. Take that for whatever you will. I have not played SWTOR yet so I may be completely wrong. All's I'm trying to do is offer common sense advice for what sounds like it makes sense to me.