Okay, I'm getting somewhere. Seeing as our other titles are okay, it must be something within DCS, so I started messing again with the view axis tuning. You can see the input value clearly jittering on this screen, and for me it affects the view yaw more than pitch or z translation. I've found that turning the "Saturation Y" down to 40, for this axis, has really reduced the shaking.
Within TrackIR I previously had to turn the "Speed" setting down, to try and reduce the jitter but I've now put this back at 1 and left "Smooth" at 50. Give this a go and let me know how you get on. I shall experiment further...