Hi guys, if any of you are experience a weird floaty sensation in your mouse, I found a quick fix that may work for you. Open your device manager and see if any game controllers are in there, you may have to enable show hidden devices.
Look for any wireless controllers (i had a wireless controller sitting in there) or game controllers and delete the driver. Overwatch thinks a controller is plugged in and applies the acceleration used to aim with joysticks (the further you tilt the joystick, the more/less accel etc.).
Even though overwatch is said to use raw input, it still applies some in-game acceleration if the game detects any controllers being used. It’s weird but it works. Felt like I couldn’t aim for the longest time. Hope it works for others.