At the end of the day, the aim of achieving a favourable Assessment Mark is to be done by ranking as high as possible relative to your cohort in a particular subject. This requires sustained effort and determination throughout year 12, all the way until the completion of your very last school-based assessment task/exam. It is a normal outcome to receive an unfavourable Assessment Mark should you not have put in sufficient effort, manifested in thorough studies, preparations and revisions. Suppose you have an exam that you did not bother preparing/underprepared for, if you end up performing at a low standard in this exam, then this can be considered a fair outcome as it is an accurate reflection of the extent to which you have prepared (if you have prepared). Similarly, in case of your school-based assessment tasks/exams, this will be reflected in an unfavourable rank, and is therefore a fair representation of your internal performance. A student cannot normally expect a favourable Assessment Mark if their rank is not sufficiently high.
Regarding the Examination Mark, one must keep in mind that performing well in the HSC exams does not necessarily mean that one's Assessment Mark must be favourable. What is guaranteed through optimal performance in an HSC exam is a favourable Examination Mark. Suppose you are a student who failed to perform at a high standard in your school-based assessment tasks/exams, but end up revamping your study strategy as the HSC exams approach, allowing you to perform well in the HSC exams. You will receive Examination Marks that reflect this performance. However, your Assessment Marks are not likely to be favourable, which is an expected outcome. Keep in mind that the Examination mark contributes 50% of your HSC mark, the other 50% coming from the Assessment Mark. Achieving a favourable Examination Mark will not necessarily guarantee you a favourable Assessment Mark, particularly if your internal performance (i.e. ranks) was unfavourable.