I'd say easier than both VCE and HSC would be the Queensland system. You have ongoing assesment all year, which includes about 2 exams and 1 assignment each semester for each subject.
In order to balance this we have a test called the QCS (Queensland Core Skills Test) which every OP-eligible student in Queensland must sit. Your individual result does not count towards your OP, rather, it is your school's overall QCS result which plays a role.
In addition, it isn't really percentage based- the majority of tests are criteria based: A, B, C, D, E. Just make sure you get A's in everything and you'd be looking at an OP 1-3 in most cases.
Every school writes their own tests for each subject, so some schools may be "harder" than others- QCS attempts to fix that assuming that a good QCS performance = good school results.