Some *objectives* are timed in the campaign. Such as protecting area X for Y seconds, or recovering X in Y seconds. Entire battles are not timed. (This is for the PC, but I think it should be the same for the X-BOX).
I'm not sure I understand what you mean with Dark Side. Playable Sith are only to the Impire and CIS.
~Dark Cupcake of the Sith