I don’t play a monk, but an ingame-friend sometimes brings his monk along. To pull mobs out of a crowd, the monk has a shorttime ae-mezz-ability which he can throw before hitting a mob, which allows to regulary pull single mobs even in dense-populated aereas.
If I understood well, this AE-mezz-ability has an ae-memblur incorporated, which let all mobs immediately forget, that one of their fellows have been pulled out of their vicinity.
About the name of that ability and the timing a more experienced player need to add infos.