Just my two cents worth.
I think that in the current climate, every major university in Australia that you go to, you will find problems with Asian stereotypes, especially in certain fields (Commerce majoring in accounting happens to be one of them). I really think that you shouldn't be basing your choice on this factor as it is going to be a problem wherever you go, even if some places it may be more pronounced than others. In such circumstances, your experience (ie your "chances of getting exposure interacting with other students") is purely dependent on your personality and social skills, and is entirely up to the individual, rather than which uni you go to. For example, if you are sociable and are able to "click" well with local students you won't have a problem mixing with their crowd. On the other hand, there are some asians that tend to stick to their own cliques and social circles. So it really depends.
As for the cold weather, its really a part of Australian life and theres no running away from it whichever uni you go to. If you're not fond of 5-6 degree temperatures, you won't be fond of anywhere in Australia during winter thats for sure (well anywhere where the major Us are located that is). This is especially more so since Australia has been having some unpredictable weather these past few years and you could be facing some cold weather even in regions where its "supposed" to be hot. For example, I live in Melbourne and at the start of summer earlier in December, we were still experiencing some 5 degree-ish temperatures. So my advice is, this is something you have to get used to and shouldn't base your choice on.
Rather, you should be basing your choice on:
1) The quality of the university
Is their teaching for the field that you are interested in any good? This may be very difficult to find out without a firsthand account from someone who has studied the particular course in the university. And certainly it would be difficult to also compare these accounts between unis, to find out which uni has a better quality of teaching. If the other forum members can't help you out, you could probably google around and see if you can find any feedback.
2) Student life
What do you intend to do once you get into university. Are academics your top priority or are you looking to get involved in student life on campus as well (for example joining a few clubs and societies)? Some unis may have a more vibrant clubs and societies (C&S) scene than others. Again, this is only quantifiable through firsthand experience, though going to the university website and looking at their student life may give you some indication of how vibrant it is.
3) Accommodation and transport
Sometimes the rental pricing for different universities can be very different as some may be located in suburbs and some located in the city. Try looking around online for rental prices around your university and compare. You might be surprised at the difference. Your rental will be a major part of your cost of living so its important to know these prices beforehand. If your uni is located in the city, you might also want to live in a suburb and take public transport.
4) Support group
I know it sounds superficial but its actually important to go somewhere where you already know people - it will help you fit in more quickly and get you on your feet faster. Remember, your friends are your family away from home. It shouldn't be decisive but if possible choose a uni where you have friends there already, or friends who are also going with you. It will make it so much easier. Another way around this is to stay in a hall/residential college as you will generally meet people quicker and feel more comfortable going into uni.
Hope that helps! I'm actually a recent graduate from the University of Melbourne (4 years in Chemical Engineering) so I know what its like to go overseas alone

Feel free to ask any other questions.
Thanks a bunch for the time in writing such a long post. Indeed you're right. Things are unpredictable as we move on. I'll refer these few criterias in deciding where to go.