Chances are people got hit by In Health too many times. Each hit lights up the AVERE one letter at a time, which boosts the damage dealt by Black Honeymoon (all five letters lit up = death). Final boss has no DPS race. She just requires you to pay attention.
Ranged that don't know what to expect will get hit by it, because the safe zone is way too small and often out of reach. It isn't really always a matter of "just paying attention"

It wouldn't be a big deal if this were like a normal dungeon and you could just retry the boss after figuring out what NOT to do, but negating your entire 41-49 run due to one wipe is going to be quite the kick in the teeth to some.