VH-VIN,
You are right in that the utility of overhead rejoin's should be discussed, but what is the alternative? I still think it should be taught, I still do them from time to time in the Caravan's that I fly to unattended and even 'attended' (in the loosest sense of the word) aerodromes.
Is there not potential for a collision in any unattended joining procedure if you fail to spot or take account of the traffic?