It is worth pointing out that one may be deemed "not competitive enough" for a lot of reasons other than age.
There is no way proving or disproving this, but I reckon there would probably be a similiar proportion of applicants knocked back for Stage 1 testing in the under 30s and over 30s groups.
Of course Qantas will be reluctant to tell you why you are deemed "not competitive enough", fearing all sorts of discrimination issues, but then again the employment process is by its very nature discriminatory, as they attempt to discriminate between those they want and those they don't want to employ.
All you can do is stop talking about it and have a go, there is no other way to find out.
No amount of discussion on Pprune or any where will provide an answer. There is more disinformation out there than can be a good thing, mostly generated by those bitter at missing out or too frightened of failure to put themselves up for selection.
If it is what you really want, then get your application in and stop mucking around - at least you'll know where you stand(eventually).