Khem is a tank. He does have a dps stance, but it isn't as good as a straight up dps companion. Andronikos is very good and his abilities hit pretty hard. Later you will get a melee dps. Its always better to go with ranged dps, because companions suck at avoiding aoe from mobs.
I'm aware Khem is a tank, hence the reason I was surprised about how well he was doing at being a DPS. But I guess that's because the planets before Tatooine are lowish level planets. Anyway, thanks.