TheSagaContinues

As I said, we usually play higher levels, but we never had such a huge issue as you seem to have, even when we have played at lower levels.  There is only so much that a rank and file Sith trooper is authorized to do for you, even if he is compliant with Mind Trick.  As for getting womped in combat, he is fodder.  Fodder call for reinforcements when they're getting womped.  What an excellent opportunity for a getaway sequence, or for a "boss" to show up.  Maybe those reinforcements or bosses focus-fire the Jedi (being the biggest threat, because you know, the fodder gave them a heads up), and the attention focused elsewhere allows the other characters to accomplish alternative goals or slip away and save the day some other way.

Another option is to just talk to your player and ask that they do not abuse any rules to overshadow their comrades.  This will solve almost every issue under the sun, without requiring new rules.  If you're feeling nasty, you can explain to them that if they do, opponents will use the same tactics when they would reasonably be available, and let them decide.  Some players like that stuff.  To be clear, I will reiterate, I agree that SF+UtF CAN be a problem.  But I disagree that a rule is needed (even a decent one like this one) to "fix" it. 

As a whole though, I find Saga to be generally well-balanced overall, without every class feeling samey.