Yes, you definitely have a chance of making a comeback. While unfavourable performance in a task worth 25% will present a negative impact on your overall internal position, keep in mind that there is 75% worth of school-based assessment tasks/exams that is yet to be determined, which therefore gives you a great chance of improving your performance in your upcoming tasks and hopefully maximising your rank.
)'s questions above are important to consider. For instance, your rank is the most important element in terms of your internal performance, and knowing your current rank is a good starting point for assessing your current position relative to your cohort. The higher your current rank, the better your current position. Conversely, the lower your current rank, the worse your current position.
Based on this, the marks that you need to achieve in your upcoming assessment tasks/exams will depend on the standard of performance that is set by the rest of your cohort. Keep in mind that the marks themselves do not matter beyond determining your rank. With that being said, at a high-ranked school, it would be reasonable to assume that you need to perform to the best of your abilities in order to ensure the best possible marks and consequently the best possible rank.
Additionally, it would be a good idea to have a look at the number of band 6's achieved in English Advanced at your school each year (which you can do on hscninja.com) as this could give you an idea as to how high you need to rank to maximise your chances of achieving an Assessment Mark in the band 6 range. The Assessment Mark contributes 50% of your final HSC mark and reflects your internal performance. Of course, the remaining 50% come from the HSC exam, and your Examination Mark will be determined according to your own performance in your English Advanced HSC exam, i.e. it is not affected by your rank relative to your cohort or your school rank. Maximising it will therefore depend on the all improvements that you make starting now and as you approach your HSC exams.
I hope this helps!