This seems to be the main thread on the issue they've been reviewing.
https://forums.elderscrollsonline.com/en/discussion/441796/fps-problem
Post any info you have there. Platform, server, location, activity etc.
Agreed, Ive never had to tweak any gfx settings in all the years Ive been playing - until Murkmire came out. Game still runs normally in every zone except Murkmire - where I routinely experience large FPS drop - it seems to occur during sunrise and sunset most noticeably - and gets worse the closer my view angle is to the sun.
I have a feel with every update since Murkmire. game is having less and less fps. today update just even made it worse