This is a major issue IMO.
It happens on the worst moments, when you need to react fast to prevent losing control, avoid a collision, get unstuck fast, unflip a vehicle.
This is why it is the most annoying bug currently in the game for me.

Patch 1.4 fixed all the issues I had with TrackIR. Zoom sensitivity, binoculars unwanted freelook and ADS alignment issues were all fixed.
You can change the sensitivity in settings like noktrum said. Around x10 sensitivity in game makes head tracking behave the same as before, no need to tweak TrackIR settings.
The zoom inside helicopters is working fine for me.