i've made this quest at 30 lvl with second attempt. Gunslinger-sharpshooter, deep of it.
At first, I've tried to kill sith-lady, then big guy, but it doesn't working. So, I focused fire at big guy and killed him before he realized that he's deadman. After that I switched to sith-lady, and pulled aggro when she has about 40% hp, used all of my cooldowns and killed her too.
I've took Bowdar to that quest, cause he has better equipment than my Corso. But it didn't help him, anyway, he died early and foolishly