Yeah, I actually had a lot of success with Leia, simply staying alive, spawning health, shielding, and avoiding the front line. It's a little harder with Palpatine since he doesn't have ranged attacks, but he has stronger attack abilities, too.
Left trigger. With Fett:
-Don't go to the front line: unlike Vader or Luke, you can't block/deflect any shots and your flamethrower is NOT a potent weapon (more on that later)
-Stay ranged: Fett's blast is a burst, and if all bolts hit, it's basically a guaranteed kill. You can have a lot of success just staying back and "sniping"
-Stay mobile and in the open: Fett was a little challenging for me at first, because I kept thinking LT would go to ADS, but of course, it's his jet pack. Use it as often as you can! Escape, get to better vantage points, etc. It's EXTREMELY useful and critical to surviving. DON'T get stuck in corridors, because you lose your biggest advantage
-Use your rocket: Fett's rocket is basically the same as the RPG homing rocket--fire it near an enemy and it will auto-track them. Guaranteed kill!
-Flamethrower is last resort/ambush tool, not a primary: The Flamethrower can do a lot of damage, but you have to be RIGHT on someone, and getting the flame "on" the opponent can be tricky. It CAN be really useful if you sneak up on a group of players, but be ready to escape/use your other weapons once they turn around