FINALLY! I read all the way back to August 2016 to get information on HOW to make the quest work! Then I moved just a little bit in front of Thassarian, between him and the barrels, and the action button appeared. THANK YOU, Crosshare!
By TheCrosshare (11,391-6·20·100) on 2016/08/30 (Patch 7.0.1)
Dismount and move towards the centre of the stones if the action button doesn't appear. Just between the grainbarrels and Thassarian.
I did not even know yet that I needed an action button to proceed. I had nothing to interact with in the area and thought I failed to receive something from the beginning when I first took the quest. At this point it is not possible to abandon it and go back to start over.
Maybe if Blizzard would add something like "Move toward him and I will give you a way to call him from the grave." Of course it would have been easiest if the action button had been automatically given to you when you accepted this quest but they should at least include wording to give you a clue that your quest is not already broken and you need something you have not been given yet.
I appreciate all the information and posts regarding the problems players have had before and after completing the quest, but my primary reason for coming here was to find out HOW to complete the quest. These players have such sad complaints.
But I have a different complaint: When Loremaster was first added, I had already pretty much completed it because back then you read each quest and followed it to the next. Questing was fun. You spent your time enjoying the lore and the gameplay. It did not require researching almost every single quest to find out where to go and what to do. It did not require addons that do help but might slow down your game. It was not a lot of work, it was just fun. I think looking up Lore and back-stories was a bonus that got lost along the way because it was replaced with looking up how to do quests or level a profession.
Unfortunately, for some reason they quit putting so much effort into each quest; I think maybe because they know players can go to WowHead or other sites and find out what to do so why take the time to explain it or add extra code to make it work now? Fun got replaced with hard work to quest and level your player as well as to level your professions. It isn't the same, fun game any more filled with action and interesting lore. A lot of the people new to the game do not even know much of the lore because they are too busy trying to level up and THAT is now time-consuming work that requires a lot of research. I wonder if now players spend more time researching how to do a quest than they spend actually playing the game and doing the quest!