I've seen a few guildies who still do not understand the advanced loot window. This video sums up pretty much everything you need to know about it. Remember, if you really want an item, mark ND (need) and it will roll for that item before people who have selected GD (greed), meaning you are more likely to win that item.
https://www.youtube.com/watch?v=zFLlX7UAAWs
Advanced Loot Window
Moderator: AOU Senator