Good timing, I was just today considering playing Diablo III on my Steam Deck (or trying to)... based on your experience, I guess that might be a bad idea to even try.
The only "cheats" I ever really saw WoW care about was botting, and that's probably easier to catch server-side than client-side anyways. Why monitor inputs when you can just see who's been fishing for the past 24 hours in a row?