And when they do pull the mob, they pull it away from area it spawned in, causing people to not get as many attacks in as its constantly moving, and in many cases causes mob to reset.
Welp, if it's causing a reset, they're probably doing it so their buddies can get there in time. If it's effecting other players and their rewards from the hunt, you can actually report players that are continually doing it.

Also, depending on how long you're waiting for, the problem might actually be that you're holding them too long. Realistically, you should allow enough time for people to get there from the teleporter (or elsewhere in the zone), and then add another 30 seconds or so. Beyond that you're just waiting for leeches.