Typical issue with Diablo 4 and GPU:
Not enough Vram
SIMPLE
I have here 4090 + 6 GHz Intel + 64 Giga RAM - never had issues but…I never saw in my live such consumption of computer resources like in Diablo 4 !!! Of course I use maximum settings without DLSS (upsampling reduces quality of surfaces/textures)
At the beginning of D4 I noticed almost 18 Giga Vram consumed by game and system !
Now situation is better but still if you have 12 Giga Vram GPU…you are on the edge with max settings.
also consumption of RAM is very big by this game.