Reduce the spawn rate of Undying Incinerators in Elreon's missions

Undying Incinerators are far more devastating than any other mob that spawns in these missions. Their range is greater than even archers, they deal elemental damage (which I guess the relic doesn't resist much of), they spam their attacks very quickly, and they can spawn in waves back to back to back with almost no other mobs.

They alone basically determine whether or not the mission is a success or failure for solo melee players. Other ranged elemental damage mobs can be difficult but none come even close to these. This is pretty much the definition of overpowered.