Impossible to complete this quest in the story!
As the High Overlord is not in the location he should be. I have abandoned the quest and restarted it only to get the same problem. Also I have changed my files to Cacheold, Interfaceold, WTFold and restarted the game as a solution found within the forums and still no joy.
The location point says he is 66yrds above me in the buildings roof 
I think not.
Hey Drewbeewan,
This sounds like phasing in Orgrimmar, likely due to starting the Battle for Azeroth questline (If you have the quest âMission Statementâ in your logs, this will be it).
To resolve the phasing, follow and complete the starting questline for Battle for Azeroth (You will know youâre finished when youâve earned the âWelcome to Zandalarâ achievement). At that point, you should be able to turn in âMeeting the Orcsâ normally.
Perfect solution, I just abandoned the âMission Statementâ Quest and all fell back into place. 
Can you please rework this quest to be functional ? i have same problem now and dont know what to do.
Hi
I made a new character to replay the old addons an ran into the same problem.
When I entered Grommash Hold it phased to the BfA start (I had not accepted Misson Statement at that point).
After a Google search told me that i need to complete the BfA introduction quests I did just that and played to the point where I could choose a zone to quest. But when I go to Grommash Hold now there are still only Sylvanas, Breka Grimaxe and Eitrigg there.