Ishamael, you do not have to fight all of them at once. Position your party out in the room prior to cultists (the one with the orcs) and keep them out of sight of the door. Then advance a caster/archer into the room and do a snipe of the nearest cultist (the one in the middle left). This will pull them to you one at a time and through the bottleneck of the door. It takes time for them to advance & you can build a pool of AP first.
