Simply allow necromancers to cast "Excorcism" right outside the dungeons entrances which will send the ghosts to chaos shrine, disregarding if the ghost have a corpse or not. Problem solved!
Personally I think it would be more effective if they made it so that if a ghost doesn't have an associated corpse in the zone, they get booted to a shrine automatically. Automate the system in my opinion.
So they can res and recall back to the same spot and hide again?
Better to send to jail where they get a Gump that has a picture of letters written in different fonts and different sizes and force you to type matching values (think 'captcha' real person validation). Once validated they can go to shrine.