I done it on 18lvl, after several times of restarting...
1. You must have "Channel the Force" ready to use.
2. Max out all possible equipment for you and companion.
3. Use stim for willpower and ready maximum affordable medpack.
4. Khem Val going for DPS mode, you for "tank" mode, use skills like Mark of Power and Guard on him. Charge you staff with "dark charge".
1. Rush into battle. Boss go under ground and strike you 250 dmg. Then attack, shock, electrocute, and melee. Hi lose 25-30% hp and go underground again, summoning minions. Now activate Channel the Force. You MUST aggro them all and kill as soon as possible. It's not hard. Overload them, then shock (one down), Force Lightning (second), melee all that left and go for Boss, help you companion. Electrocute boss (Channel the Force recharge your Electrocute).
2. Now he lose another 30, and another time go underground. Repeat step 1 and kill second wave of minions. You companion almost dead now and soon perish. Focus on boss, after he kills Khem Val and goes for you, use medpac (if needed) and finish him off. You will be able to make his last 25-30% hp disappear.