When using a joystick to fly helicopters, your maximum tilt and jaw speed, the rate at which you can control the heli, is lower than with mouse.
This means you put yourself at a disadvantage by using a controller that _should_ be more suitable. Raising sensitivity only makes the game react harder to small inputs without changing the reaction to max input.
I'm not talking about the fact that mouse gives you more precise and quicker response to your actions - that's natural. I'm talking about max turn rate with a joystick fully pulled to the side compared to a mouse moving as "fast as possible".
I see no reason why the game would be designed this way, so I'm assuming it's a bug.
PS: I searched but could not find an existing ticket for this, but please delete it if there is one.