It would be great if you could have a Dungeon Delve Mode. It would work one of these ways, either:
- You can't leave the dungeon until you've beaten the core quest/boss at the bottom of the dungeon. (Special auto-save before you enter.) OR - Leaving the dungeon resets the dungeon, but you still get to keep any experience/loot you got. Respawned mobs don't drop loot a second time.