Tank companions rule and anyone who says otherwise has clearly no idea how to use them. That being said, on a Jedi Knight, which has no support roles, tank companions are less than desirable.
And that being said, Lord Scourge is the one companion I use when doing dailies at level 50, deck him out in my offspec DPS gear (in DPS stance, with a Focus equipped) and he can put almost as much hurting as Kira while being A LOT more survivable (and easier to gear up).
not sure how you are managing that, my companions die in seconds when trying to do the dailies and if i haven't killed the strong that practicually one-shotted my companion, i will be close behind, then in came a commando and just AoE'ed the lost down and just had the strong to take out.
The Jedi Knight needs a good AoE, maybe give the force sweep/smash ability a dot as well as what it currently does, that does its initial damage and then the same amount of damage over 15 seconds or something.