Your build is fine, Khem does start to suffer alot at those levels. Just get by with him for now and go do your class quests, you should get Talos real soon and he was a game changer for me. I keep him in his healing stance and am almost always near 100% health at the end of a battle and I just keep moving. Since I've gotte Talos, I have little to no downtime and no problem with any mobs.