I run up to the top level where the boss 2 and 3 are without agroing anything, then I pull everything there and then jump down to the entrance. Then I wait for everything to come to me.
Just make sure that you don`t stand with your back to the mobs lol.

BTW some mobs won`t be pulled, it leaves like 4 packs because they stand to far away to be pulled by the mob zerg.