I'm not sure it would be the best path.
Okay there is less jobs on offer with an Econ degree, but a Masters in Commerce does essentially over qualify you for graduate positions. You might struggle to find work after too because your a tad over qualified for fresh graduate work, but (i assume) you don't have the work experience needed for a position which is above a graduate.
Also, don't most Masters degrees require full tuition fees upfront? You'll be looking at in excess of 40k most likely, and your HECs debt (if you have one), and no guarantee of a job. I think you'd be better off looking hard for work, (maybe look outside econ field too and see if there are positions available that would ordinarily be commerce degrees that don't seem as stringent) seeing if you can complete say a sub-major/minor or another major that makes you more appealing to a commerce job, and if all else fails after 6 months or so, then possibly consider doing a masters. I'd research very hard/ie. speak with business to see what it is they want, and if they have no interest in masters then don't do it/ and then decide from there.
http://www.gradconnection.com.au/graduate-jobs/economics/ has a whole stack of graduate opportunities available. A credit average is not something to be looked down upon, its a very good mark in many employers eyes.
Good luck!
