Just to throw another spin on it...I don't know if this is entirely a Qantas problem....employment policy has a lot to do with it as someone correctly pointed out above. Airlines do not employ people into CAREERS now, they employ "resource" and it is all about cost.
Many people who are employed are seduced by the "glamour" (I know, I know) of working for an airline. By the time reality sets in, they use up all their sick leave, then resign and go elsewhere..this is certainly true in the LCC model. Management see this as a good thing as they have a continual stream of new enthusiastic types wanting the glamour and willing to sacrific all for the nice uniform.
On some of the larger airlines, they don't leave, just get sourer and sourer to the detriment of the customer and the image of the airline. Management with no clue try to improve morale with floggings and obviously the effect is reversed.
So in the end, management are to blame, but sorry team, some of the blame also lies with you. A strong united workforce should have a strong united voice. Do you have one?