It worked for me, I changed my sense with that, it sorta multiplies ingame depending on which mouse setting you have it set.
I went ingame and pulled the sensitivity bar all the way to the left, then pressed the right arrowkey 3 times.
After I did that, I went into C:\Users\<user>\Documents\My Games\Dishonored\DishonoredGame\Config and opened the DishonoredInput.ini. In there, I changed it to MouseSensitivity=20.75
It changed my ingame sensitivity for me. Even an adjustment of 0.05 changed the sensitivity for me.
Thanks for your fast reply btw!