I'm old enough to remember that when Diablo came out, it seemed to be running too fast. This was before 3D video cards were mainstream (which happened with the Voodoo and Quake in 1997 maybe?). I was working a lot with blitters at that point and running into speed issues on the Mac because Apple liked to release machines with half-width busses, which cut memory throughput by almost half. I'd be lucky to get 60 fps on…
I wrote a bot for Diablo 1 (https://sourceforge.net/projects/projectsolo/). Due to the way the game uses older Windows modes for the palette, the colors never come out right in screen captures and also get messed up if you alt-tab. IIRC I had to use an API call dating back to Win16 to get the raw bytes, and I used artificial color for the visualizations rather than figure out how to obtain the actual palette.