@Hazard: I play with a vision range of 25 and haven't had that problem. Are you sure it's not just some hard to spot enemy that wasn't in LoS until later? I guess you could spot an enemy in the open and move back until you don't see them anymore?
@Dioxine: Yeah, I generally agree that it would be good to have a "config mod" that sets the gameplay relevant options properly. Having configs as a file that can be exported could work. You already export yours often enough with the executable

Although in that case it's the whole config, including resolution (which would cause my game to crash as my laptop can't handle resizing the game in full screen) and debug mode (= no quick save anymore

). Having a proper setup where you can list only the options that should be changed would be much nicer.
However, for things like vision range that affect performance, it can't be in a mod
unless it's also easy to change from the default/mod value for the user in the GUI. Asking users to go in the mod to change values defeats the purpose as it's no easier to change it in a mod than in the config file.