I think what Qantas are trying to do with the changes is reward fliers more and reward those who make points with credit cards, etc less. Fliers with silver status or above will be earning more points even on discount economy fares - while the value of all those points earned from credit cards / etc is much less. I think Qantas have a large number of frequent fliers now who never actually fly Qantas (except on reward tickets), and the changes are an attempt to rewards those who do fly more (particularly on high revenue tickets).