If you're set on doing law, your order of priorities should be
1) Law/X double degree at Monash - because you're guaranteed a law degree (obviously depending on whether you pass everything, but I mean in the sense that you don't have to do any further tests like the LSAT to get into law)
2) Deakin law - not Group of 8 but still a decent law school. Make sure you have good marks, excellent co- and ex-curricular activities like mooting, as well as work experience/volunteering if you can get it, and you won't be at much of a disadvantage.
3) Undergrad -> JD at UoM - because whether you get into the JD depends on how you do on the LSAT and nothing is guaranteed (unlike the other 2 options)
edit: in the current job market you're not guaranteed a graduate job no matter what uni you go to. You're better off choosing the option that'll get you a law degree in the first place and working on the other aspects of your resume.
Was talking to an ex-corporate lawyer a couple days ago who's friends with a recruiter for a top law firm, who recently rejected a UoM graduate with a high distinction average, so nothing's set in stone