well, i think everyone has different capabilities, therefore i don't believe that any subject is harder than the other its just the way you as an individual think, for example there are seven different types of intelligences, these determine the way we learn, if you find that you like the more english, legals SaC, well english based subjects you most probably hate maths and some sciences, i for one think chemistry is hard but then again i don't like maths either so maybe its just cause i can't wrap my head around the whole number thing. someone who loves maths will probably find it hard to right an essay in the usual 40 minutes so its just an individual thing. with the scaling thing i wouldn't pay much attention to since your only really doing the hsc to get to the next step i.e uni wateve, the most important thing is just to maximise your marks in the exams, since thats what your atar is practically based on.