in the actual HSC exam they dont go on a word length - everyone writes different so thatd be stupid - they go on how many pages in an exam booklet u use. forget exactly how many it is (11 or somethign like that?)
anyway, bout the quality/quantity thing - was talkn 2 my dad bout that (hes a senior HSC english marker) & he said that while its true that the examiners r lookin 4 quality, since they read so many they have the tendancy 2 start thinkn that if u havent written a substantial amount then no matter how good it is u musnt have covered enough stuff in the essay - whether thats true or not. so, always better to err on the side of caution i reckon! anyway, surely no1'd sit there if they had spare time during their exam and do nothing - there's ALWAYS something u can add 2 make ur response better.