I'm level 79 and I have always found nightsisters an easy enough target.
What I do is take the protection off mt and daka and then let zombie taunt. I stay on zombie or random other nightsister with protection with basics til cooldowns are gone.
Then at some point I use chopper's cleanse on zombie. Ezra's two specials (call assist from hera) and and Hera's special (call ezra) and whatever other attacks you have should quickly kill both daka and talzin before either can revive someone.