You "roll" for a chance at each piece. If it's loot you want, roll need when you can and greed when you can't. Last night, I got all but one piece in a dungeon. A lot of times people pass, they just don't care if they get it, don't have room in their inventory, don't roll at all or I got lucky. All I ever do now is to turn it in for seals, but there are those who upgrade their current armor and jewelry with it. Bottom line, it's luck of the draw, but need tends to trump greed.