I just entered with a guild member in the Quest 'Servants of the Overlord'. Unfortunately several of those chests could only be looted by a single player. And yet I thought it is a game that support partys
Actually the other player saw the same list then me in the optional chest behind the red door and looted all. The second time I looted all at the chest behind the blue bar with the lever and he found only an empty chest. As I suppose this is not as intended I bug reported it.