You have to be outstanding to get the Dean's Scholarship. Like. OUTSTANDING. I know people who missed out on scholarships (not just Dean's scholarships, all scholarships) with USYD Business with ATAR's in the 99's. You will need a high 99's ATAR and a proven history of extra-curricular involvement, leadership, the whole shebang to be even in the running for Dean's. They conduct interviews when finalising their decision, usually with about 10 really outstanding applicants, so you need good interpersonal skills too. I have no idea how they make their final decision though because the quality of applications is really freakin' high!!!
I think this year there were something like 40 undergrad scholarships given out by USYD Business. There were only about 10 given out to the value of greater than or equal to $10000/year. The rest were Merit (6K/year) or Entry (6K/first year only). To be pushing for anything more than Merit, you'd need a higher ATAR and (presumably) a wider variety of extra curricular/leadership/volunteer/work experience. I have it on good authority (i.e. from the kids who got bigger scholarships than me) that USYD Business REALLY VALUE WORK EXPERIENCE IN BUSINESS!
Having said that, I have friends who got 99.8+, had heaps of EC's and only got Merit scholarships. So who knows how they make the final decision.
In terms of writing your application - make yourself seem as amazing as possible. It may seem like you are a massive tool when you're writing it but I really do think you do need to look as flashy as possible! Also use wide margins. And small font (but not too small, I think I got to about size 10 or something
). Write as much as possible, use full sentences. Don't go back toooooo far in EC's but if you've done something consistently for years make a big deal out of it. I'd recommend getting someone to proofread it too!
Good luck!