I've always understood loot to work on tags. The first five people and their groups to tag a mob get loot. I box 8 in two teams of 4, so I'm always good as long as no one else is tagging the mobs.

I'm not 100% sure it would work, but you might want to try arranging your toons over 3-4 groups and 'disarm' some of them. What I mean by this is to make them not attack and therefore not tag a mob and push it over the tag cap before the other teams get a chance to tag. They should get xp for the kill by their teammate and theoretically everyone should be able to loot. Considering the time it could save you I think it would be worth the time to test it.