The megapull mentality exist on wow mythic+ too, the point of the mentality is that it easier to clamp up as much mobs as you can and kill them all together than focusing down them 1 by one, honestly no dungeon atm could work with that same system because the mythic runs use also some clever skips in between mobs thanks often to the terrain itself, something that we lack and unless the reward is considered worthy ppl would avoid it most of the time, take notice that mythic+ became "interesting" only because they give you crapton of loots otherwise they would have suffered the same fate of pandaria/wod challenge modes, which honestly is a damn shame