Does an MMO need a story? No. No game does.
Bioware has blurred the distinction between games and movies. This is a trend in all Bioware games, not just TOR. Bioware always had games with great stories to tell, but with more recent games the focus has shifted far too much into the story telling direction.
When creating a game the first and most important aspect is gameplay. Story telling always comes second. Bioware seems to have forgotten about this.