For 2 reasons. 1. It's got [b]way[/b] to many bosses. It has 1 enemy/puzzle encounter and after that 4 boss encounters with nothing in between. It's not a lot of fun to constantly be pressured by boss fights. 2. Those 4 boss fights are all incredibly mechanic heavy. The Warpriest is realistically the only boss in King's Fall that can be defeated without all 6 members. Golgoroth has too much health to lose DPS from even one person. The Daughters and Oryx have incredibly complex mechanics that require the entire team to be alive for. If lose even one person, especially on heroic mode, it may as well be an immediate wipe. In every other raid you can lose a person and still have hope to 5 man the encounter.