You need to feed your Khem some forceusers so he can grow big and strong. Im in mid 30s and he is my goto champ if things go bad. I dont even have him geard up to his lvl (no headgear, no implants, no ear...just noticed I still have a belt for lvl13 on him) and he just doesnt die if you dont pull 2 elites. Now I just send him and force storm the area until everything is dead.
Just use static shield before you send him in, put your HoT on him and DPS. easy.
Also if you are lvl30 and you cant afford spending few credits to gear him you are doing something wrong.