PSA: Mouse Input is broken in this game (looks similar to bad frame timing)

Are you playing on Mouse?

If so, that's the cause. 

Mouse input is broken, which ruins an otherwise well optimised game.

For reference, I easily average over 100fps even on the bigger maps, but panning the camera with mouse input makes the game feel like it's running at 15fps despite no drops.

In-game reporting confirms it's running perfectly, as CPU/GPU are always rendering within 10fps of eachother.

Connect a controller though? Buttery smooth camera panning, and easy to track enemies. No hitches or stutters, just butter.

I've tried:
- All polling rates, from 125hz up to 4000hz
- Toggling raw input on/off
- Enabling/disabling Nvidia reflex
- Changing USB ports, changing to different mice, wired/wireless
- USB power saving etc all turned off
- I even tried a driver/Nvidia CP restore, but as controller is super smooth, this was a long shot in the first place

Unfortunately the game is unplayable using a mouse on PC due to this. It's next to impossible to track targets, and you quickly get a headache from the micro stuttering when panning. The effect is very similar to Helldivers 2 on PC, when you turn off 'Mouse Smoothing', as that game has serious issues with raw mouse input.

Happy to hear suggestions on how to fix this.

Mice tried:
- Keychron M4
- Logitech G305
- Logitech G604
- Razer Naga Hyperspeed
- AttackShark M1

I've also tried on an entirely different PC, same results. OLED as always exhacerbates the issue too, due to the awesome pixel response times. I fear many won't see it due to slower LCDs.

Specs are:
5700x3d
3060ti 8GB
32GB DDR4 3600 CL16
AW3423DW (Gsync module version)

This is on a fresh Windows install, up to date drivers (tried DDU as well to be sure), but honestly since it's running beautifully with a controller, this looks to be purely a mouse input issue.

No other games exhibit this issue other than... Helldivers 2, and Battlefield V. BF1 is butter on mouse, as are BF3 and BF4. Helldivers 2 can be fixed by turning on mouse smoothing in game.

I almost bought a GPU upgrade before testing the Xbox controller, saved myself £600.