Multiple Rare monsters with "Heals Allies" can heal each other and brick an encounter.

Ran into a iron forge room in the Temple where the boss had 2 Rare monsters next to him. Both had "Heals Allies and Suppresses Enemy Recovery"-mod. Both were healing each other and the boss, effectively making them all unkillable especially when the 2 Rares really loved to stand in the middle of the room filled with lava.

Suggestion for fix: Make any Rare monster with "Heals Allies" mod be immune to healing to prevent this from happening. Especially now that "Monster Effectiveness" is a thing, healing Rare monsters might become potentially map-bricking encounters.