People complain about bullet sponge bosses, so Bungie design bosses with cool new mechanics (eg Qodron, Skolas) People bypass these boss mechanics with Gjallarhorn and burn the boss down as quickly as possible. See the problem here? Gjallarhorn is massively OP and Bungie would have to design every boss fight from now until the end of the game around an OP weapon from year 1. It needs to die for the good of the game.