Working as intended.
This is a new mechanic in boss fights. Slow the whole system down for a slo-mo dramatic effect type thing. It’s going to be huge for the industry because it’s going to help churn systems.
Adding to this that myself and two of my friends have the same issue. I have a 3080 and my friend has a 9070xt.
What’s funny is that this didn’t happen back in actual Legion, so it must be collateral damage caused by graphics updates in later expansions that hit this room as well. The graphics changes aren’t an issue in a solo/legacy content setting either—both because combat ends so quickly and because there’s only one player present—but now that Remix has made Legion ‘current’ again and the room is once again packed with players, that + the new graphics settings (compared to the 7.x days) are proving to be a problem that’s gone unnoticed until now. 
and it’s ugly, bad looking graphical effects causing it to boot. I had the same issue in Suramar at the Nightmare root quest giver in the north east corner of the map. As soon as I left the Pepto-Bismal spill effect everything went back to normal
Getting this too and only in Xavius’ room. GPU temps spike up to 80+C and it sounds like my PC is about to take off. I have an RTX 3060Ti
I think it’s actually the gray background in the area. Maybe the fog. Maybe the fact there’s a whole scene being culled while the fog is there. I dunno. It’s bad. My Mac (a maxed out M4) has fans whirling on this boss.
It’s definitely the heavy fog. Even my 5080’s fans start cranking, and no other game I have can do that right now.
I went into Xavius’ room on non-remix and let him attack for awhile and there was nothing. GPU temps were normal and everything was fine. I’m not sure what is causing it in Remix.
Oh wow that’s very strange. You’d think it’s the same.
So I think it has something to do with the nightmare color effect same thing happens in suramar where the satyr are placing totems down.
This happened in the original legion as well. I just cast spells like crazy and hopefully don’t die. The lag is too much to actually move out of anything so it’s kind of rng dependent.
Yep, only place in WoW that freaks out my GPU. That room just pushes it to 100%. Temps just rise, fans kick up to 100%, GPU starts to throttle. Thankfully the fight is short in remix.
My entire game freezes during the dragon boss in Darkheart Thicket, but I don’t have much to say for the Xavius raid boss.
It would be, if you took a full raid of players in there outside of Remix. It’s the same room, but outside of Remix you’re running it solo instead of with ~20 other characters adding to the load.