I don't see many people with this armor and I get a lot messages asking where/how to get it so I thought I'd post a quick guide.
[i]"To find this armor set travel to the Warrior's Planet and head north, past the Buried City. There you will find the Ivory Graves and at the center of the Graves, a Wayshrine, the first of many. Fill the ewer with Light from the basin at the First Wayshrine and continue to fill it at every Wayshrine until it is full and you reach The Traveler's Rest. Once at the Temple pour the Light into the Key, this will open the door to Barkhan's Sanctum. If you complete the pilgrimage properly Barkhan's set will be in engram form on the mantle. Before leaving be sure pay your respects and don't forget to leave the ewer.
If you're curious who Barkhan was I can only tell you a little of him: he was a Warlock before Warlocks were called Warlocks. He was fascinated with the Traveler and wanted to understand it. Barkhan believed the Traveler choose the Red Planet for a reason, and he worked tirelessly to find that reason.
Good luck finding his armor, I hope it will serve you well... and keep the sand out of your boots."
- Mikal-55, War Cult Altus[/i]
[spoiler][b]TL;DR[/b] This set decrypts from Sublime Engrams. I think there is a higher chance of getting the Barkhan Dune set if you take the Sublimes to the Reef, but I cant prove this. [/spoiler]