I don’t know the specific mob, I move quickly and on foot in between so I don’t always notice right away. It is always in Terrace of Ten Thunders, and not related to quest items because it happens farming mobs there while not on a quest. It happened on four different characters, so I was using all baseline BM hunter, shadow priest, ret paladin, and balance druid abilities. I don’t know if it’s related to tinkers, either, as combat issues in the zone have been reported prior to remix, but cold front, hailstorm, explosive barrage, meteor storm, slay, and meteor storm are the only ones that would probably cross over between all characters, however it’s possible some of them did not have those when it occurred if they were not kitted out yet.
I also just found another thread from early in the event so it sounds like a common issue in this area:
Could have been this mob for me, as well: