One thing is the massive number of insta-kills in that fight. You can get crushed by a tower if you don't move the right way quick enough. Or you think you move the right way on the double fall and move right into the path of the other one. Someone can crowd you in with red circles of death you just keep getting hit by until you die. You can get REALLY boned if you're the group by the door and he does his flaming arm on that side, since groups are encouraged to stay by markers as much as possible to be ready for sand spheres and to be in the right areas for golems. That one really hurts because the attack doesn't kill you. It's that fast-acting debuff. People can live if you can get it cleansed quick enough, but it's a very slim window.

Another thing is the murder dominoes that can happen with just one mistake from a single player. Someone from A brings their stack mechanic over to B's spot? That whole party goes down. Or as I mentioned with the red circles of death, someone crowding multiple people and giving them nowhere safe to run.

A third thing I've noticed is lag. I call this raid Laganastre because at some point nearly every raid, someone goes "Is anyone else lagging?" in either party chat or alliance and a chorus of "You too?" or "Yep" follows them. I usually only see it on Mateus, but occasionally Hashmal as well. And lag in that fight along with the mechanics it can cause you to mess up can be a raid killer.