Aussie Andy,
One data point does not cut it mate
That "data point" is two people dead.
What that accident shows is that see and avoid is not 100% successful. The next line of defence in our new airspace in Class E is TCAS/Controller alerts, and unfortunately that comes down to whether the transponder is working or on. With no radar it is just down to TCAS (if fitted). Because radio frequencies are not denoted or delineated, listening out or making broadcasts will probably not be a factor.
Everyone knows that see and avoid is not 100% successful - it is a human limitation.
Everyone knows that transponders are not 100% reliable - it is a human and mechanical limitation.
Everyone knows that IFR and VFR traffic can cross paths on climb and descent to hemispherical levels - it is probability.
These are the three holes that need to line up for a collision in Class E Airspace. As an ATC I see the last two happen nearly every day. I also get pilots never sighting an aircraft I've given a radar position on. All it takes is for these three to line up. And, outside of radar coverage with no TCAS, there is only one line of defence.
In Class C airspace, a VFR aircraft will be known to the system, it will be radar or procedurally separated from other traffic. It is only when the ATC system fails (multiple layers of defence), and when the VFR enters without a clearance, that we get to the same level of protection in Class E.
There is less risk of collision in Class C than in Class E. NAS2b replaced some Class C with E. NAS2b, in that airspace, is less safe. A comparison with the US is not required to establish this fact.