The scenario for the quest ‘’ The Medallion of Dominion’’ is completely bugged for now.
Kael’thas isn’t spawning when you enter the scenario, which makes the quest impossible to complete. I had to leave the scenario and re-enter it at least three times to get Kael’thas to show up.
Besides that, the cutscene that should play at the end, showing the defeat of Kel’thuzad, is being automatically skipped and we’re immediately teleported back to Sinfall, with no cutscene or anything.
Here for this bug, and also at the end of quests character gets stuck.
I had not problem with Kael’thas but the cutscene didn’t play, I was teleported to sinfall.
I can’t even start the quest for the last chapter. I’m renown 23, currently on chapter 8/9, but there isn’t anymore quests for the campaign available from anyone.
Yes, this quest is full of bugs and I hope they fix it soon! 
Can confirm, happening to me too. Really glad to experience this EPIC CLIMAX after 2 months of waiting to see how the story concludes. /s
This is par for the course.
Bug 1 - Initial entry into instance, Kaelthas did not spawn. Had to leave and return to get him to spawn.
Bug 2 - While fighting Kelthuzad, near his defeat instance shut off and was ported back to Revendreth with the quest “The Medallion of Dominion” completed.
Cutscene upon turning in quest did play though and no issues with receiving rewards, except maybe the weapon one should of been Normal equivalent for this long of a campaign system. Most people have outgeared it by now.
The cutscene didn’t play for me and I’m stuck. I can’t move or anything 
Additional bugs to add to this:
Well, you cannot kill the necromancers because Kael’thas is the one who should kill them. You just have to lower their health and then Kael’thas finishes them off. But apparently he’s not spawning when he should. I had the same problem earlier, where Kael’thas wouldn’t appear and the necromancers wouldn’t die. I had to leave the scenario and re-enter it at least three times to get Kael’thas to show up. Perhaps doing this will fix the problem for you, but it’s just annoying that this keeps happening and that Kael’thas doesn’t spawn on the 1st time you enter the scenario.
Same here, having the same problem and cant find the quest giver…
The cut scene did not not play, and I was pacified and could not use any of my abilites, although I was still in the necropolis in the scenario.
lol is there really no possible way to reset i died too
I just exited the game and when I logged back in I was out of the scenario and able to go turn in the quest.
having basically the same problem with the maldraxxus version.
Art of war maldraxxus campaign quest - Support / Bug Report - World of Warcraft Forums (blizzard.com)
I had this issue too and the problem was that I never completed the questline for Laurent earlier, this was basically a side questline while leveling that I had skipped. You can see the full list of quests for this questline here: https://www.wowhead.com/quest=57531/an-unfortunate-situation#comments
I can’t even start the quest its not showing up at all for my Priest
Yeah, the quest won’t even appear for my alt. I did the anima and soul weekly but there’s nothing
The quest doesn’t even appear for me either, the other two weekly campaign quests show up but not the chapter 9.
come on blizz been like this for 24 hrs i wait for my scenario !!!