Nick, sorry fella but let me WEIGH back in.
1) In VRS, increasing the collective does not make the aircraft fall faster.
In an established VRS raising the lever further will make the a/c accelerate downwards, fall faster, as you are stalling more of the rotor from the root thus exacerbating the ROD.
2) In a hover, you cannot get VRS until the aircraft has an appreciable rate of descent, usually beyond 700 feet per minute, likely about 1200 fpm or more.
If you have a rate of decent beyond 700' per minute you aint in the hover but descending vertically.
3) In a hover, you can descend vertically without getting VRS.
Of course you can.
4) In incipient VRS, you can raise the collective and fly up out of it, if you have enough excess power.
Of course you can very, very carefully but I dont recommend you try it to often.
5) At high altitude, it is harder, and takes more descent rate, to get into VRS.
Explain please, at higher density altitudes you will be using higher power settings to hover. Less power margin to try to recover.
6) Most events people call VRS are actually where they haven't sufficient power to hover, so they settle down and hit the ground and call it "settling with power" and "VRS" and it gets captured that way in accident reports.
I think you are confusing overpitching with? Surely everybody looks at the graphs in the manuals for HOGE. 5%, 10% etc
By the way the bloke who taught me POF was an TP from ETPS with more than 1 masters in aerodynamics. It scared him!