Clinton,
Quite right, in the AAT every "defendent" I have seen is more focussed on arguing the Regulator is presenting evidence that is flawed rather than mounting a credible defence based on evidence that is irrefutable such as using the "R44" as you rightly put.
It becomes a "we said, she said, they all said" type anecdotal rant rather than substantive evidence.
In most of the cases where substantive evidence has been presented by the defence the AAT has found against CASA.
Over use of expert witnesses seem to cloud the issues and the matters become mired in conjecture.