I play a scoundrel, split spec between healer and dps. I use Corso Riggs, the ranged tank companion, exclusively and it works just fine. Versus 3-4 normal mobs my level I dont have to heal him, and he keeps aggro. Vs a single Strong enemy i dont have to heal if i keep up my own dps, vs 2 strong I will heal and dps. Vs 1 Elite I will mostly heal and throw in dps when he is high on hitpoints. I have no complaints .
Ive geared him up every chanse I get, often taking small upgrades for him over badges as quest rewards, and using badges for gear for him when available. He uses several orange items that i keep updated with new mods etc. He has quite a lot more hitpoints than my healer/dps character and much better damage mitigation. When I get aggro from mobs I die *much* more quickly than he does, thats for sure.