Dps is fine until around Alderaan. It starts getting tougher there. Should be around lvl 30 then. Use Mako for dps. I switch to tank when I picked up Gault. Around 30, tank is really good with a dps companion. This goes all the way to the end. Like Spitoc said, field respect is a very nice tool to have. I will tank when I am running on planets and switch to dps for flashpoints and pvp. Learning to do both will teach you a lot about the class.