I've read somewhere above that the dungeon (can't recall the name) where 3 guys with daedra hearts are in, will reset every 7 days. Although I spent 7 game-days (using the rest-wait function) it didn't reset. Am I missing something ? Are the dungeons trully reset and how ?
You need to be outside the dungeon, and wait at least 7 days without returning. If you wait 6, then see if the baddies are back, the counter will reset.
Try fast travelling to a city, e.g. Whiterun, then wait 8 days before fast travelling back to the dungeon. It should have reset with baddies, and loot. Which makes where you're talking about particularly awesome, as it also contains Ebony and Gold Ingots, and some enchanted weapons.