With older type helicopters with limited max power, in VRS pulling more power did increase the ROD. However when the Wessex 5 came on line, especially at low weights, by pulling max power it would blast its way our of VRS & climb. Do that in a Whirlwind & big trouble!
A few years ago a Puma 330 made a steep slow night descent to a ship & got into VRS. From 500 feet to splash was about 15 seconds & that's with 2 experienced Puma instructors on board! Luckily both survived.