Hi there,
When I am in a raid my fps is around 120-130.
Whenever a boss is pulled it drops to around 40-50.
I have never experienced this issue before in any of the previous raids.
I tried disabling addons but nothing changed.
When I put the graphics to 5 instead of max I managed to get 50-60 which is still very low
In m+ I never experience any issues.
It has been most sever on Vigilant Guardian and Anduin
CPU : 3700x
GPU : 5700xt sapphire
Combat will always lower FPS due to CPU and if there are multiple particle effects going out at the same time they will tax the GPU as well. Can you go to old raids and check if the FPS drop there has changed to same levels as in the new one?
As I said I haven’t had this issue during this expansion at all and haven’t touched my settings.
Its normal that frames drop yes but not by this much. I changed the spell density but that didn’t seem to work either.
I checked my temps and load on both GPU and CPU and everything seems fine.
Drastic FPS drops that remain unaffected by lowering the actual display settings are very often the result of performance-hogging addons, which especially in raids can have a rather substantial impact on the game. I’d definitely recommend to clean them out fully, and see if that won’t get things back on track. 
I seem to be around 70fps without any addons active.
However I can’t pinpoint it to any specific addon. I am running WA, DBM, Plater, Vuhdo, Details. Could it be that all of them together just lower my fps this much ?
It seems to get worse when more is happening in raid (like dmg or adds spawning) which should be a normal thing.
Is there a way to check what each individual addon is doing at a certain time ?
Its very difficult to test this.
DBM is NOTORIOUS for being a resource and FPS hog.
I also noticed my CPU usage during raid is around 20-25 percent and my GPU about 50-55 percent
While in the open world CPU remains the same though GPU goes up to about 80-100 percent while most the time just being at 100.
I used the addon “addon CPU usage” during an lfr raid.
This is the result :https://pasteboard.co/KbavfoK0NcOn.jpg
It makes sense for Vuhdo, WA and Details to be at the top I guess. The question is is the amount of usage they have problematic or should this be fine ?
Plater is most likely the one causing FPS drops from my experiance.
Gonna give addon CPU usage a try