At the end of the day, the responsibility to be educated and informed is the voter's. The government can take steps to help, like school curriculum and what not, but at the end of the day if you choose to go out and cast your vote then it's your job to make sure you can do so competently. I agree that the government should take steps to resolve confusion about the Westminster system. In the same way, if you and I are doing some electrical work and you're about to cut some wires, I should make sure the power's switched off for you. But it's your own ass on the line, so you'd damn well better make sure yourself. When something like this happens and you don't like it, ignorance is not a defence.
More importantly, I don't think you're giving your fellow Australians enough credit. Essentially, you're saying that, on the whole, none of you can be fucked to skim a Wikipedia article before heading to the polls. I'm sorry you feel that your country can only handle what the nice, caring overlords decide to spoon-feed them. Seriously, give me a break.
Maybe instead of bitching about the government failing to inform you that this was a perfectly legal possibility, you could take this opportunity to try, in your own way, to help educate other people. Phone your local schools and ask about the civics curriculum. Tell them you think this is a problem and make suggestions to fix it. Take ownership instead of saying, "No one did my job for me, how unfair."