Yesterday i forgot to set the Lootmode to need or greed at the beginning of the Mission.
Later (End of the space part) i changed it from round robin to need or greed, but this change took no effect during the whole time incl Rebecca.
It was a Guild group, so we trade the items, when someone was in need of something.
This is absolutely the opposit to the posts of the others here.
In Guild Wars the Dungeons do exactly this. The chests at the end spawn a number of random items, each one assigned to a specific player so only they can pick them up. It'd be nice if that happened here, at least for the boss drops. Locking the loot setting once everyone has entered an instance is also a viable option, though you'll still get the slime that always picks 'Need', which might force you to restart the run just to have them kicked from the team.
That said, most folks are doing these runs for the Marks of Valor, not the drops. After all the runs I've done, I've picked 'Need' only once on a single item that rounded off my Mk X collection of weapons. Otherwise, I've yet to see an item worth grabbing. I have enough credits to buy what I need on the Exchange, and I can use the Marks to get the superdoopa cool stuff from vendors. Loot is the least concern at this level of the game.