Would a specific ability to scout really be useful? I mean, once all the dungeons are cleared, they sorta become deadweight and useless. Unless there are randomly generated dungeons periodically.
No ruins or dungeons should ever reach the state of being permanently cleared by natural means. The monsters, undead, insects and other evil beasts actually seek dark, damp and unholy places... much the same way humans seek farmlands and rivers.
It should be possible for a channeller to cast spells which helps prevent these dungeons/ruins from being repopulated such as a powerful holy spell; a gate locking spell; an earthquake spell; etc., etc., .
Also, I'd prefer if most dungeons would regenerate eventually once they're cleared. And they needn't be populated by exactly what was there before, either. Sometimes a dungeon might slowly become repopulated over time, and maybe sometimes a powerful creature will move in overnight. This would keep the world alive longer.
I completely agree.
I like your idea of regenerating dungeons but I think there needs to be contingencies, otherwise you might end up with a situation where a player will "farm" dungeons, which damages the atmosphere that dungeons are meant to create in the first place. I think that, for instance, dungeons that are near civilized areas should very infrequently replenish, if at all. Dungeons in distant wildlands, though, should replenish on a regular basis and even follow a sort of "succession" in which stronger individuals succeed weaker ones. I also think that any cities, outposts, or mines destroyed and left derelict too long should also become dungeons, the strength of the dungeon being contingent on the size of the ruins (or the terrible way in which is was decimated. Undead minions after a terrible slaughter?)
Hopefully a formula will be used to determine when a dungeon is repopulated.
These variables should include:
Any nearby civilized areas which decrease the rate of repopulation
Any locking or holy spells which decrease the rate of repopulation
The actual depth of the dungeon which increases the rate of repopulation
The actual degree of evil and unholiness which exists at this location which increases the rate of repopulation (A dungeon with a long history of horrific evil will be difficult to control... even to the point where it's not safe to have civilized cities/structures nearby.)