Can't get 80? That's crap ... as many have already said. One of my students a few years ago got 97 in General Maths and got the Premier's Award for Band 6 in all her courses.
Dumbing down is certainly possible. Have a look at the original 2001 paper or the 2002 paper. I think they were pretty meaty. Compare them to the 2004 paper especially - VERY straightforward.
Politik ... thank goodness someone else in the state realises what I've been trying to say. That UAC (which used to be UCAC) are basically doing the same thing they've been doing since 1986 - using some sort of complicated formula to generate an aggregate score, UAI, TER, whatever you want to call it. Up to and including 1985 the HSC was awarded as an aggregate score out of 500 - you're best 10 units, and English had to be counted. That was fine for UCAC (or UAC) but then the board of studies went to individual subject marks in 1986 and UCAC felt they still need to have an aggregate to admit students into Uni or College. The buggers are still doing it, and I reckon they need to move into the 21st century. 1986 - that was even before HECS came in, when University education was free! (Well, very cheap)
Of course, if you're doing the HSC this year then I would suggest that you DON'T look at actual HSC papers until about 4-5 weeks before, so you've at least got some exam papers that you haven't already seen. There's no point doing the same papers over and over again. Save last year's paper to the night before and do it yourself under exam conditions, then check it yourself. By then you should be completely on your game and you'll have a pretty good idea of how you'll go.
Hope this helps!