Charlie,
Some things to remember about VRS is that the airspeed and ROD required to enter VRS change depending on the aircrafts weight, density altitude, and rotor loading.
A lightly loaded helicopter is more likely to get into VRS at a slower ROD, but conversely will experience ETL and leave VRS at a lower airspeed. The same helicopter with a heavy load will need to be descending at a higher rate in order to experience VRS. But then this helicopter has to travel faster to achieve ETL and escape VRS.
A heavily loaded rotor versus a lightly loaded rotor works in the same fashion. The higher the rotor loading, the faster the ROD must be for this helicopter to enter VRS but the airspeed must also be higher to experience ETL and escape VRS.
The higher the density altitude, the greater the ROD must be to enter VRS. But again, the airspeed to achieve ETL and leave VRS is higher.
Vorticey,
Yes, the rate of descent that you will enter VRS decreases slightly as you increase forward speed, then it increases slightly before hitting ETL. This has to do with the fact that your rotor is now tilited forward and your vertical downwash is lessened. Since your downwash is now slower, you will experience VRS at a slower ROD than at 0 airspeed.