BackPacker, to correct your assertion that helicopters need >500ft to autorotate we can autorotate from the hover all the way to the moon. Almost
It is a matter of energy management from three sources: height, airspeed and rotor RPM (RRPM). The ideal is to arrive with zero airspeed at 5-10ft agl then sacrifice the RRPM to cushion the touchdown.
To the OP, a helicopter behind you in the circuit should have no effect whatsoever. Should you follow or cross a helicopter flight path then be aware of the tip vortices which can produce a noticeable bit of 'wake turbulence', but this is all dependent on the size and speed of the helicopter along with the size of the aircraft.
Whopity, where and when was the fatality that you refer to please?