I read this on this board somewhere, but I figured I would pass it along since it sped up my looting a ton. Put the group on master looter, rare(blue) or higher. Put all of your characters on "pass on loot" except for the one you want to do all the looting.

Then you have one character who loots everything except blues, which you can master loot to the one you want. I don't do collection quests, this may affect those.