I second this, really wish I could up the sensitivity. I don't understand why that option isnt available. It would make the combat a lot more fun.
HERE LIES THE ANSWER:
GO TO THE GAME IN YOUR LIBRARY AND CLICK PROPERTIES
Go to the controller tab and make sure steam input is enabled
Then either click the underlined "Controller Configurator" button on the controller tab, or click "View controller settings" on the game's library page.
Edit Layout and then Joysticks
Change the right Joystick to "Joystick Mouse"
Now mouse sensitivity affects the joystick
You're Welcome
Edit: Make sure to add the Right sitck click command, for some reason it erases it when changing to Joystick Mouse
