I'm having a similar issue. My frames have been cut in half since patch 2. Though, to be honest, it's still playable at about 28-35 fps in Act 3. I have not done any real testing under DX11. My results have been Vulkan based. I've tried the current proton experimental as well as the newest GE proton (Glorious Eggroll), both are about the same. Oddly, DLSS used to give me about 15-20% more frames, and now it seems like it does nothing at all to improve performance. I've had no real issues with conversations in Vulkan. Also, it's not overly choppy, just severely reduced FPS.
I've come across some reddit posts indicating that clearing some of the game area caches help, but it did nothing for me.
I'll try DX11 later.
Mint 21.1
Nvidia 353.86
3080 FE 10GB
No mods
