[Artifact Warrior] Impossible to beat the final "boss" or "mob"

[Rohu]

WoW Freakz link: Can't find it. Im sure its there, but when i do the scenario no name of it appears.
Bug description: In the first part of this scenario, you are transported to the Broken Shore, where you meet with some Vrykul's, then you have to fight some Demons, the imps do insane damage, so the npc that are helping you sometimes die easily, they hit almost like 20k. Then the Valkyr comes down, in that moment another demon appears kind of big, but, he's easy to strike, so i killed him easily, the problem is when Malgalor shows up, i start atacking him with all i have as a warrior, but still, he kills me like in 2 hits with his magic. I've tryed protection and didn't work, so im not sure of what to do anymore... I leave there a screenshot of the insane damage that Malgalor does. Hope you fix this, it's been like that since the 7.2.5, a lot of people have complained about that, but no one has done a post here, so, yeah.

Also, thanks for the hard work for the 7.2.5 content, love you all.
Proof: https://imgur.com/a/bWzW3MN

[Virtuos]

Did you manage to get thru the Quest yet? I have the same Issue and noone could help me yet nor i found any information about his insane damage and unavoidable Fel Firestorms