The Ring of Blood: The Final Challenge not properly working?

Hey me and a group of friends have been trying to complete this last quest to this quest chain. Yes we are getting the tag, we are the ones starting the quest to kill Mogor, and we are killing him in the center of the ring, but we are not getting quest completion. We've done this 3 times now and have yet to get any progress, some info would be very much appreciated as we cannot complete this quest and have no clue why.

And here is proof of me getting the kill, and the tag, and still no quest completion.
http://i.imgur.com/oYRAcw5.jpg

bump.. still have not had my ticket answered, nor found a solution. Upon killing Mogor, even grabbing the tag, I've still yet to get the quest completion, as well as with relogs and every other possible thing I could think of.

I have the exact same issue, just tried it twice today.