ive been meaning to write this for some time but just havent got around to it. also, this is my first time writing a guide, so please, bare with me.
i learned this while playing the closed eu beta and it has been a great advantage! it turns out that enemies in MS spawn randomly based on a sort of ticket system. this means that it is subject to abuse
lets say we have a map with 3 floors with enemies on them. notice how you can stay on one floor and kill but it seems that mobs spawn fewer and less often the more you kill on that specific floor, and that there are hordes of mobs on the floor below. this is because of the ticket system! lets say that there are 30 spawntickets in this map and that at first they are split up equally on all 3 floors. when you start to kill to kill the 10 mobs on one floor there will be 10 free spawntickets alllowing for 10 new mob to spawn randomly on each floor. this means that the mobs doesnt necessarily spawn on the same floor as where you killed them. at some point there will be no mobs to kill on your current floor and youll have to move up or down to kill more.
the advantage here, is that you can team up with others in or out of a party and organize it so that you each take one floor and kill everything on your individual floor, purging the map of enemies and freeing spawntickets. doing so will make mobs spawn on all floors more or less equally and make exp come more steadily, even faster as you constantly have something to kill, rather than kill, climb, kill, climb.
i hope you find this somewhat comprehensive and maybe even usefull.