Basically the angels give you buff. One is a movement, the other is a stunning one, super useful for the bags of HP coming your way: those are the real damagers.
The only trick is to never leave less than 3 persons around the angel, or he will wipe your team clean in a single map attack. It’s a lonely angel!
Well there is another trick: your character with the stun buff shouldn’t end its move near one of the your guys who isn’t immune to fixed damage, or it will be a bit sucky.
You got Luna, right? She is a must get out on this map; she turns the angel’s attacks to a mere annoyance.
Otherwise, just make sure you put all your heavy damage dealers out, and they can attack every other turn depending on the angel current immunity.
I did it with all physical.
Also the angel will attack whoever is the closest to him, preferably flying units.