Done this "ridiculous" pull some time ago with heros. I just let minion master tank, frozen soil up and as an elementalist, echo savannah to mob. In less than 10 secs, "whoops, where did the mob go"
In Slaver's Exile, the monks from other mobs always run to help other groups if they're close by and a lot of times they will help even when they're nowhere close. You need to pull the groups farfar away, then get a tank or MM to block them on the corner. Pulling them helps bunch them up on the corner for a quick kill. Try to kill the enemies as fast as you can before the other monks arrive to help with heals.