Hmm, I know I made a suggestion within a suggestion thread before about when a Well breaks/disappears etc.
Think it goes like;
When a Well Breaks/Disappears... another monster spawn happens AFTER you killed the Well monster from the item you drop into the well. Like a Swarm modifier for Maps, but, happens when the Well breaks/disappears.
No, not a boss... maybe it could be an EP of some kind? This would be better in my opinion.
As for a "Well Detector" class... I would love it to be Guardian, I mean, everyone hates a Guardian, so it is the least class character to be used... also... a Guardian should be able to identify the "Evil Well" presence in a Catacomb.
now... you can also have this for a Paladin.