.....let's assume they had 1500ft/min ROD which is more realistic in the R22
Doesn't sound like fully developed VRS to me, not in any helicopter.
I agree with ShyTorque. The first time I went to the Robinson safety class in the 80's the instructor (Hi Rod!) demonstrated it to me. Not only was there no shaking or vibration (he just really nailed the middle of the vortex I guess), but the VSI quickly pegged at 2,500 ft/min. Then a little forward cyclic and we flew out of it pulling I guess a couple G's.
A lot of people will have a sink rate of 500-1,000 ft/min and some vibration and say they're in FDVRS, but I think they just have enough of the disc sticking out into the airstream that they're getting some net lift to keep the sink rate low. It's *hard* to find the center of the downwash and stay in it (unless it's snowing!).
In that R22 demonstration the transition from OGE hover to falling out of the sky gave little warning: I usually describe it to my students that it was like "stepping off a roof". Lots of fun, when you're at a few thousand feet!