MIss Behaviour just a comment on your comparison between QF and DJ fares. I am not sure what fare booking class you used in your comparison but I suspect the more restrictive fare conditions apply to these fares.
I travel quite a lot on both QF and DJ paying for my own (usually heavily discounted) fares. Both QF and DJ offer terrific promotional fares from time to time which I take full advantage of.
From my experience, the biggest difference between QF and DJ is the ability to cancel discounted DJ fares (subject to a $30 cancellation fee) with the balance held in credit and available to be used within 12 months from the date of ticket purchase even for the very cheapest internet fare.
I agree with you that it is often possible to find QF fares below DJ fares on equivalent (or even more direct) flights. However the headline fare alone does not tell the entire story with the devil in the detail.
The deeply discounted QF fares are generally confined to the internet Red e-Deal variety which are sold on a 'use it or lose it' basis. So even where the cheapest internet DJ fare is more than the QF fare I still chose to travel on DJ because of the ticket's greater flexibility - if I find I am unable to travel on a particular flight I only lose $30 of my fare and not the whole lot. I have no trouble using the balance of the ticket price within 12 months.
To me this is a significant difference in the fare structure of the two airlines that is little discussed.