Yeah, bad players do happen but Mass Player killer on purpose is a different story.

Example: Last fight, when you run out and stand on the pads. They would spawn their add, then kite it to the nearest group (ours) and let the dullahan cleave our entire group.

On the fire bomb pull before King Behemonth, they ran out into the fire and danced until they died just because.

On atomos they ran into the fight started it, pretending to be ready, then would run out as a group of 8 and watch the raid wipe.