I’m having CPU issue with Diablo 4 (i think). The game is only running on one of my CPU cores, which is causing it to run poorly. I have a decently high-end PC with an Intel Core i9-12900K CPU and an NVIDIA GeForce RTX 3080 Ti GPU.
I’ve tried all of the troubleshooting steps that I’ve found online, including your pinned message above for users with Nvidia cards, checking my CPU usage, forcing Diablo 4 to use all cores, and updating my graphics, bios and board drivers. None of these steps have worked.
Basically the game is unplayable at times. If I reset to defaults and make no changes, then play it works well for a short time, then the game becomes laggy, rubber-bandy and unplayable (all of which are technical terms… 
)
Anyone found anything that works? I don’t think I will be able to keep playing like this much longer honestly. #bummer