Don't stand at the entrance of the room. Move in and jump/run away from the main group, so everyone doesn't get to attack you at once. There are pillars around the central area of the room, so stay on the outside and you will cut down ranged attacks significantly. Also, the group will spread out a bit as they follow you (especially if you summon your creature and demon), so you can turn and take out one or two at a time.
If you need to get away from the divine in a hurry, you could rush attack an archer, or something, at least while there are any left.
You do not need to conserve health potions at this point. There is a delay before you can use another health potion, but I think you can use a rejuvenation potion right away (though it doesn't heal as much as a straight health potion). Even level 1 of the healing spell would help, if you get out of direct melee combat to use it.
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