Since I got a good Initiative roll my first playthrough, I decided to go back and reload until I got a bad one for this encounter. I didn't change any of my party, their equipment, or their prepared spells ie the closest I could come to a blind run. Isobel only had 3hp left by the time my party's initiative came up on the reload I decided to go with.
The encounter was saved entirely by one spell, Sanctuary. Larian changed it from "Wis save to attack targeted creature" to "targeted creature can't be attacked" and when she tripped on Jahera's ice it bought me 2 rounds that she couldn't be targeted. I had been using this busted change to keep Gale alive prior to this.
Party: MC Paladin, Shadowheart, Gale, Karlach.