One does not simply "dial down" Mary Sue, and frankly... I don't think it is too Mary Sue-ish. Often Mary Sue, now at least, has just become a label people put on something they do not like. But if they are capable of dialing the epic factor down, sure, go ahead.
Lastly I don't see why anyone would take the class stories out of the game. They're the main selling point. Take that out and SWTOR is... To put it mildly: Screwed.