If you want to do Medicine (extremely difficult to get in) of what use are lightweight subjects like PDHPE and Visual Arts to you? You see what type of subjects successful students by and large in the past chose. They don't do wimp subjects.
You should choose subjects that are relevant to your goal, and not do subjects just because you love them or think you are good in them. Most people nowadays have a different view from mine, which is rather old-fashioned. Better talk to your parents as well. In year 10, you are a making very important decision but for which you may be too young and immature to make a right one.
What you are saying definitely has truth to it, and a majority of the successful 99+ ATARs are derived from high scaling subjects which are done well by the students who have chosen them.
But there is the rare occasion that students do achieve an extremely high ATAR with what you refer to as "wimp" subjects.
My school is in the rank 100s ~ 200 and last year, which is recent and relevant to 2015/2016 and closer years, there was a boy who had Eng Std/Adv (don't remember), Mathematics, Drama, Art and I believe the last one was...either a Science or Hospo and he achieved a raw ATAR score of 97. It is definitely achievable, but may be difficult in terms of scaling. This goes for other subjects like the notorious Business Studies and Legal Studies, which have assisted students in achieving high 95+ ATAR, heck, there are some amazing people like Drifting who did English Standard, General Maths, Business Studies etc who achieved 97.
I think subject combinations are endless. And at the end, if you know you are capable of struggling through subjects you hate and not good at (which is what I'm doing in Physics) and believe you can still maintain a high rank, then go for it. Otherwise, I believe a good balance of subjects, whether "wimp"y or not, will help you build your path