I had just finished completing the Tartarus dungeon, it took me almost 2 hours and when I finally beat Hades, I didn't receive any drops at all, and the quest for the dungeon still wasn't completed. All that happened was I gained experience and gold but no rewards. The quest still said to defeat Hades, and now Poseidon and Zeus stand in place of where Hades used to be. So I pretty much just wasted 2 hours of my life doing this dungeon to receive no rewards whatsoever.
This also happened on a separate occasion for a boss fight in Azteca, I fought and killed the boss but he respawned right after and the quest wasn't completed.
