First try, first map, dungeon was totally empty, including no chests, and not resetting after waiting a while.
Then a guildie got me into a second map where there was a group already working on a (non-empty) version. Joined, did some of the later fights and puzzles, go to the last room, couldn't loot any chests, but still got my "daily completed" notification (and it was indeed completed).
It doesn't help that you need to do 4/4 to get the daily. In the past, when something bugged out, I could easily do another task or kill a veteran in WvW or something like that, and still get the daily done. It's a downgrade that there now is NO choice on what to do to get your daily done. I would prefer it if the daily was more like the current weekly or the previous daily: do "login" plus 3 out of five (or 4 or 6) to get it done.
Maybe look into what is put in the daily (and if that's working correctly, there are plenty of bugs mentioned on the wiki page) before throwing it into the rotation.