This is what I’ve gathered so far, hope it can help you get some decent stability in Diablo 
Also, haven’t had a crash now ~12 hours with all of these settings.
Set Power Consumption under nVidia control Panel to “Adaptive” - This is a big overall boost to stability and fps. Do not use “High Performance” as it makes the game run slower overall somehow.
Set Fps Cap to 60 Fps Maximum under Diablo 2’s Video Settings. - This Helps A lot maintain fps above 30~60 and it increases fps too.
Set Vertical Sync to ON, helps smooth out everything graphically, improved the performance too a little.
Uninstall all programs that use overlays and Streaming services. Xbox game panel/twitch so on. (nearly doubled the Fps)
Removed Geforce Experience Panel(helps a little)
Done a Disk Driver Uninstall and reinstall newest graphic drivers. (Helps a bit, and makes game run a lot more stable overall, also on little bit on the fps meter. )
Disabled the Integrated Graphics to only use primary Gpu(Gave me over 5fps increase overall permanently)
Set Scaling to 50-75 in the game menu, (helps quite a bit on the fps overall)
Run in Windowed Mode Maximised(Helps Tremendously)
Turn on Dynamic Resolution Scaling(seems to help a little)