I'm using Bind Sight with a Cral Ligi Guardian under the world in the northern area of the zone (through the tunnel). There are a good 50 mobs roaming about under the world. Screenshots if needed. These include "an underbulk"; "a grol baku", "a cral ligi". Seems to be more mobs underworld than above it. Playing on Bristlebane.
This used to happen in the old days in most zones. I can't believe it is still happening today. Perhaps they could add a Z axis flag in the code and do a check every few minutes. If a certain threshold is reached then the mob could kill itself like the cleric summoned hammer kills itself.