While I agree with this thread in there should be a time limit on these specific dungeons. It would be nice to see a dungeon that does have a time limit. For example a bunch of miners getting trapped in a cave that will be that is going to be exploded and your job would be to save the miners. If you manage to save some random miners they leave and extend the time limit by X amount. This IMO is a proper way to design a timed dungeon, because it is more engaging for the player and allowing different ways to tackle the dungeon.