I don't think they should change it. The SC gives dropouts something to show employers, while those continuing on will do it easily. The SC isn't insanely difficult and to be honest if you're spending more than an hour a night studying for it you're studying too hard. (Of course if you're dropping out it's a different story altogether.)
Also, yes, it is a state, not a federal, issue, but it has been proposed that the federal government use various things like the power of the federal purse to force the states to standardise the education system. Not done yet, but I know Labor and Rudd want to standardise a lot of the curriculum, while Howard wants to standardise Australian History only =/