Are you talking about that?
The problem I see with content like traditional dungeons or quests is that they take some amount of development time, then players do them once in a few minutes and will never do them again. It'd be more time efficient for devs to add repeatable content (perhaps dungeons in the style of a roguelike?) but I'm not sure how well-equipped we are to handle such a thing. Sounds like it would be heavy on the server.
The trick is to hit the sweet spot of pre-generated and randomized content.
Make a set of 100 pre-generated dungeon level areas. After that, have a randomized baddy placement algorithm for the entirety of the system. Have the server present a single set of 5 random levels out of the 100, shuffling it on a daily basis. In this way, you would have 20 days of absolutely new content at minimum... or if you weighted it (with rewards in certain rooms, for example) so that some showed up less often than others, you could have a few months of content without it getting old.
Play of these generated dungeons could be graded on a leaderboard system - how many deaths a player took to get through the area, how many baddies they killed, how much loot they picked up... if they got through without dying, what their time was per level or overall... there's lots of ways to make it competitive. Imagine getting a score out of 5 and getting tokens for your level of completion, and then having a special store you could spend the tokens in.
Additionally, you could plug in limited time level sets, seasonal events/baddies, special rewards... Or even charge gralats to run through the dungeon more than once per day...