So, I've been complaining about ESO performance for a long time, and even dropped my sub months ago because of it, vowing to not spend another penny on this game until ZOS fixes it.
Today I finally got around to buying some canned air to blow the dust out of my computer, and holee mutha what a difference. Whereas Cyrodiil (NA/PC/Kaal) had been a slide show for me during keep battles when the server is pop-locked, today it ran smoother than it has for me in months. I could see every skill animation, the terrain passed smoothly, and every player on screen appeared immediately. I checked the patch notes and there’s no mention of performance fixes so it looks like a simple cleaning drastically improved my game performance.
Now before you accuse me of white knighting, there is still plenty of skill lag and bugs for ZOS to address. I couldn’t get Forward Momentum to fire a LOT for instance.
tl;dr clean your system. It may help.