Benefit.....Raiding/PVP end game? I guess just to spite blizzard and their new perks your whole guild could leave the guild at 90 and raid by calendar invites. A guild is not some perk whore (except for alts) it is a social group (to some degree) that plan events and work together like in raiding or pvp. And yeah have group will travel was awesome.... but oh well, maybe mass teleportation for mages? Could happen.