I really liked the "challenge" coming from the Bardam's Mettle dungeon. It made us play three mini-games to complete a boss fight. Henceforth, I want to see something that is different in our future dungeons; other than the monotony grinding of dungeon monsters.
I would like to see us trying to solve some interactive mechanics along the way. For example, jump puzzles - everyone will try to get to the top of hill/cliff/mountain to clear a path to the next boss. If someone cannot get up there then the player that could can active a teleport node on top to get the remaining players up.
Another example, scavenger hunt, search for clues (like Satasha opening) to unlock a hidden door and failed to do so will open a trap with 2x more monsters.