Okay, I was out of the loop then!
I think this issue is still a bug, at the start of the flight it runs smooth, later on when I could not even enter back to VR, on monitor both the GPU and CPU were underutilized at 25 or less FPS, and I crashed out ahead of the landing.
Then I loaded a flight with the same FBW A320, same location and landed in VR smoothly. Afterwards I checked and my GPU was pegged at 98-100% and indeed most if not all threads on my 7700k were showing 80-90% utilization.
BTW I am very much aware of the limitations on those four cores, I set my glass cockpit refresh rate to low, no multiplayer traffic, also closing all hogs like browsers (I also have only 16Gb RAM) and refrain from stuff like listening to music recording my flight. 
But I get triggered when people say it is that much of a bottleneck, like you get 18fps because of that. Below 100fps it is fully OK in any applications (with the exception of AC Origins/Odyssey, there 60fps is the max), and there may be occasional low 1% drops, rest of the time it is still the GPU that bottlenecks me in most games. DCS VR runs 90fps easily when GPU load eases.