Shadow Crash

I’m not sure if this is a bug or not. My current group is mostly casters, all level 84 with around 1000 health, I’m currently built around a water salamander so every creature is defending/casting on every turn.

This spell has wiped out my part a few times and a few of those times, it seems as though it was early in the fight so I hadn’t cast too many spells. I was wondering if it is calculating the spells that attack all enemies as 6 casts of a spell instead of 1.