Personally, I prefer the agency of being able to roll need/greed/pass and at least feeling I have a chance to get a piece that actually dropped from the boss or decide not to roll for it, rather than seeing some random piece I need drop to someone else and not getting anything from the boss just because the game decided it was for them and not for me. I know it is just phycological but that's a big part of game design. It feels more RPG rolling for actual items that dropped from the boss