The scholarship is a bribe. You shouldn't be basing your uni decision based on such a small sum of money (a decent scholarship is at least 5k, otherwise it's just tokenism. It should be able to pay for most of ur HECS). You could be earning many multiples of that working instead of taking on an a extra degree you don't really want (and having to incur a debt for it!)
Also, if so many scholarships are being handed out (relative to other unis), it devalues the scholarship. It no longer makes you stand out if many many other students have been awarded the same one too. This is similar to Science degrees that have "Advanced" tacked on to the end. IMO, they would be better off using the scholarship money to fund prizes and industry training/projects to form better links with future employers. In that way, at least those students taking on more degrees have some idea of what industry is.
I think if you have a good idea of what you want to do, go the uni that can get you there the fastest (and with minimal loss of teaching quality, prestige, etc). If you are undecided, do a combined degree. Either way, your preferences should be towards Monash. Melbourne figures highly in Australia because of it's strength in research but that isn't really relevant to an undergrad.
Also, the top employers will interview high achieving candidates from all unis. For the large part, unis are recognised as being top because they attract the best students. All the other stuff kind of follows on from that, like excellent research facilities, industry links, etc. So in the end, it comes to down to the quality of the students, not the university. If you are good, you will make it from any university.
However, I think a Maths/Actuarial program at UoM is a good idea as I think that's the right order in which to become an Actuary. The actuarial syllabus was first designed for Maths Honours students entering insurance companies who worked full time and studied the actuarial maths part-time by correspondence.