I'm not doing the HSC (VCE student here), but I don't tend to memorise full essays. I usually have a general memorised essay structure or possible sentence structures (i.e. say for the introduction, I tend to have a very similar sentence structure, modified for each essay type and altered depending on the topic). However, this is more achieved through writing multiple practice essays, not through actually rote learning it. I've found that this has worked really well for me, and I've been able to do well in English so far without memorising full essays. I think overall memorising can be a bit of a waste of time, since you want to show the examiner or teacher that you can apply your knowledge to a range of topics with unique insights (it also takes away from essay practice time). They can easily tell when someone has just rote learned an essay and tried to slightly modify it to the topic (which can be a problem, as a memorised essay might not fit the topics given, which could lose you marks if you try to somehow modify it to suit it). That said, I know for some people memorising essays can be really helpful in achieving high marks, and some people are really good at it. However, I don't think it's a must when it comes to essay writing. I'd focus on memorising essay structures, sentence starters, synonyms, and ways of phrasing language to ensure your essay is as analytical and insightful as possible.
