I tend to use Khem as a tank. Send him in first to attack the mobs and then aoe lightning or use your other skills. Usually don't need to worry about healing yourself this way and he helps slightly with dps.
Yes, you lose him story-wise so far but after doing KotFE chapter 9, you can get him back (outside of the story) from the terminal in Odessen.
Actually, you lose all your companions (except extra comps like HK-51, Treek, CM ones, etc) in KotFE and gain some back as you progress including companions of other classes. That terminal in your base can be used to summon all your default class companions back though. They would have the same influence as they did before you started the chapters. You may want to max Khem's influence with BT runs beforehand though. I don't remember him gaining influence there after I summoned him back.