Same issue here since the beta, the 1st person tank aim sensitivity is easily 1/4 the effective sensitivity of 3rd person, gunner, etc, and this isn't due to the turn speed cap. While there is a Tank Aim Sensitivity option in settings, both 1st and 3rd person are coupled with no way to adjust both to your liking. Tank Aim Sensitivity also maxes out at 2x, and should be increased, as to go beyond 2x requires manually editing the PROFSAVE_profile file.
Unsure if it's related to the bug but in the settings menu there are two Vehicle Mouse Aim Sensitivity sliders, and they appear linked (a change to either one affects the other) but display different values.
The first is under Mouse & Keyboard - Vehicles, the other within the Vehicles - Control Settings subsection.
