I have totally decked out Doc, Kira and Rusk all with purple lvl 50 gear, best implants, ear pieces mods if needed e.t.c.
With Doc its god mode, I just jump into any packs no matter what mobs they are and just walk out un touched, no fear of death.
With Kira, she does some insane dmg, but more single target of course, but elites go down so quickly I am usually at 70%+ health.
Rusk is an AOE machine, groups just get smashed with him along, and his single target DPS is as good as Kira's, He is hitting for 3k.
They are all good, at 50 and still going through my clas story line and quests I find im using them all to be honest, when they are all decked out they are all pretty bad*****
I favour Doc just because its brain dead easy with him along.