I've never found more than one piece of gear from a single dungeon. It's always 0 or 1. So if there is a limit, it seems pretty pointless to kill remaining bosses if you find a piece of equipment from the first boss for example. I've seen many people leave after finding an item. A dick move, but I understand if it's like that.
Or is there some unlucky streak prevention that increases the odds of an item dropping every boss kill that doesn't get you loot?