As seen in another recent post. I have the same problem. See below. Thanks
"I completed the Quest “The Defias Brotherhood” Which made me turn in the mysterious message obtained from the defias Messenger. After I turned in the quest. There was no follow up quest, but there is supposed to be one to escort the Defias Traitor.
So I have no Defias Traitor. I cannot do the Quest. I cannot see the quest. And there is nothing allowing me to fix it. Plz help."
same. figured this was the case, googled to here. looks like no deadmines for me ;p
The defias traitor quest is given by the traitor himself, who spawns near the bottom of the ramp at the tower. Only one can be spawned and if you don’t get him you have to wait till he gets to moonbrook and despawns.
Oh and if you’re in a group make sure you are all beside him or the away dude will fail the quest.
Worked for me on Pagle, look at my previous comment and hopefully that helps
thank you, this worked. 
By “this worked” do you mean the solution is just to wait at the bottom of the tower a long time and hope the traitor respawns? The quest shows as “Failed” in my quest log. Do I just ignore that? Or should I abandon it?
For the record now, I’ve waited at the bottom of tower twice with a group that needed the quest, and both times I didn’t get any credit for escorting the traitor. 
Yeah, it seems very bugged for me. He spawns and I can’t talk to him at all. 
Sorry I should have mentioned this as it happened to me. You will have to abandon the quest and the reaccept it from the traitor.
For anyone looking for further help: I saw the last player leave the tower with the traitor. It takes about 4-5 minutes to complete the trek without many mob attacks, maybe 6 minutes with bad luck. Just wait at the base of the tower and the traitor should spawn, offering you the quest.