Focus your hits on the banshee. She can't take too many direct hits. Also, I've noticed the alchemist is an easy kill if you focus on him as well. With this in mind if use a heavy single hitter, like Lady Azov
See I focus one or the other, however Lilith just tanks the damage. I use the Prisoner, FFE, The Madam, and KP. Sadly, the Banshee's basic attack adds Perfect Immunity to all of them so passive disable never triggers.