I usually pop my bubble on my companion and a hot right as the fight starts. Then I DoT up the mob and damage skills until the companions bubble de buff is off. Replace that, replace the hot, top off the companion, and repeat. DO NOT forget about CCing mobs. If you are fighting mjultiple mobs use your whirlwind to kick off the fight. Its a 60 second skill that most mobs can not break. Taking a mob that actively does damage to you and or your companion is a smart idea. If needed before you damage the CC'd mob heal yourself and your companion real fast.
Ive never used any companion besides Khem Val and Xalek. You should only be using tanking companions really. Make sure you are gearing up your companion as you level too. The quest rewards that offer companion gear are usually the best way to do this while leveling.