The HM on Scalecaller Peak is bugged. Whichever player has to run to the geyser for safety is not guaranteed to live even if everyone did their job and they made it into the geyser with plenty of time to spare. I had heard from other players that if the player who was going to the geyser got there last then it would not glitch out but this still happened to our group last night. This fight is difficult enough as it is so it is essential that the mechanics actually work when they are supposed to otherwise us players are just wasting our time.
Our run in which we made it the farthest last night was ruined by this bug and it was incredibly frustrating.