I discovered this problem a couple of days ago while running a hard assassination LDoN. It was just me in this LDoN, four boxing my warrior, cleric, ranger, and mage.
I made it all the way to the end of the LDoN and pulled the Mad Goblin Boss. The fight was down to the wire. In the end my warrior died when the boss was at 0-1% health.
The boss then began killing the rest of my characters. My mage and ranger quickly perished.
The boss then turned on my cleric and died on the damage shield. So, at this point everything was dead and only my cleric was left standing.
I checked the loot, and it was the perfect totem of endurance my warrior had needed.
So I went to rez my warrior so she could loot it. My warrior got the rez and started loading the zone, but instead of popping up where she had died it immediately kicked her back out of the LDoN, because the LDoN had been completed with the boss kill.
It was the same story with the rest of my characters. Everybody was locked out of the zone and unable to loot, except for my cleric.
So in the end my cleric was forced to loot the item.
I'd suggest making it so characters can be rezzed back into an LDoN after the LDoN is complete, as long as it's within the 30 minute grace period. That way everybody gets a fair shot at the boss loot.