I dropped my weakest subject straight away when I went into year 12 and it worked for me as I was able to do better in (almost) all my other 10 units, it really depends on if you use the extra time in both school study periods and at home due to not having to worry about another subject. A lot of people may do their first assessment and see how they go, then decide. for eg my school we always have our depth studies as the first assessments for the sciences which are worth 40%, so a lot of people did their depth studies to see how they went and just dropped their lowest subject accordingly.
However, the downside is that while you have 2 less units to worry about, you can't afford any bomb-outs in your assessments and in the hsc, but given you're a top student it will be less likely, especially if you also concentrate on those subjects with the extra time. But honestly your subjects are great, don't worry about what other people say about it.
