It's happened to me 3 times so far that when loot drops in a dungeon that can be used by tanks and lancers/dragoons, that despite the fact that I was playing as a dragoon the "need" button was grayed out, and the best I could do was "greed" the item. It stated that the reason I could not "need" it was because I was not the right class...
This happened in Brayflox Longstop and Haukke Manor.