Well, I can't get past this part of the quest.
I sucessfully got the key killing the Vosh Rakh guys, but when I enter the Greedy Gut it's completely empty.
I saw a guy with this same problem over the XOne Tech Support Forum, so maybe it's worth checking.
Edit: So... I abandoned the quest and tried a different approach to it, by trying to steal the key off Sergeant Vulmon, but I emptied his pockets and got no key.
So I went to kill the Vosh Rakh dudes again and... They just vanish mid-fight, for no reason and I get the key anyways. Still, I went to the Greedy Gut and it's still empty.