You Teleport melee away while you strip ranged of armor to cc them.
As for retribution answer me this, does your tank not getting damaged at all? Is it immortal? Because in my experience it is getting damaged just fine and even killed at times, yes enemies prefer softer targets, but they won't shy away from bashing the tank if that is all what's readily available and you can make it that way with positioning, armor stripping and CC.
Like I went against Mordus in Tactical and it was a difficult fight with him at full power and yes eventually tank got killed and it had a whole shitton more HP and armor than other party members, so even if others get damaged, tank also takes a good punch.
As for Retribution itself and maybe things like Leadership and so on that start with tiny %, with mirror existing it's hardly an issue, because you can instantly dump a bunch of points where you want to make that ability worthwhile. There is no other real solution, you could say make earlier levels give more %, but then you will start having various bastard builds cropping up as well as diminishing returns on investment which is kinda counter productive.