Not sure if this is a bug, but it certainly seemed like it. When the first boss throws down his spears, they started blasting out the stacks of fire damage. We barely put a dent into the boss's HP, and had 7 stacks of fire damage from the spears. They exploded every few seconds, but remained until we finally broke one, then he launched more, and each one of them kept putting stacks on us until we wiped. Multiple attempts at the boss, but could not stop the massive stacks of fire damage from the spears...

I've never had that happen before, kinda curious.