very few tanks and some of them suck in dong their job

[Vaer]

What is the benefit of this "sac-pulling"? I am genuinely interested. I tried coming up with scenarios where it would be preferable to simply killing the mobs but came up with nothing. Maybe you could enlighten me?

Skipping dangerous mobs. You can have someone pull the group and the rest of the group run by to a safe spot so when they reset they don't aggro and the party gets passed them.

Another practical application used in other games is that you only want one of the mobs in a group (Say a named mob) you can have someone else pull the named mob off the sac puller and the sac puller will get rid of the rest of them and the party won't have to deal with them by basically resetting them on death. The sac puller then dies in a reachable spot. Raise also teleports the dead player in ARR.

Those are two things I can think of off the top of my head. Might not work in ARR but just what it is used for in other games.