Unable to Progress in Deeper Into the Darkness Scenario

If you are not able to progress through the quest Deeper Into the Darkness to complete your Whispers of N'zoth questline that grants the legendary cloak, Ashjra'kamas, Shroud of Resolve, try the troubleshooting steps appropriate for your scenario:

• If you are not seeing any NPCs in the instance and have the quest A World Worth Saving active in your quest log:
  1. Drop Deeper Into the Darkness
  2. Complete the quest A World Worth Saving
  3. Pick up Deeper Into the Darkness again 
• If you can't interact with the shrine in the scenario after being ported to the instance:
  1. Use your hearthstone to leave the instance
  2. Go to Uldum and fly to the Halls of Origination
  3. Enter the instance again
• If you are able to get through part of the scenario but it becomes stuck and you do NOT have A World Worth Saving:
  1. Abandon Deeper Into Darkness
  2. Pick it up again immediately
  3. Return to the scenario and try again