The question, for me, comes down to why you're doing law and how much you're weighting the legal qualification in terms of importance/value (or even, what you're thinking in terms of employment). I mean, at 23/24 years old, you've got two degrees, you've just finished studying hard for 6-7 years including Year 12... you face a choice... "Wow, I'm glad uni's over, that was tough! Okay... now, I can practise law or seek full-time employment in the legal field or even pursue journalism as a profession... Or I could study intensely for a little while longer!"
Let's be real, my phraseology is obviously leading you in a particular direction... Who knows, perhaps you're more academically inclined than I am, but I feel as if the majority of people would probably be sick of uni after two degrees. The curveball here is if you were thinking of pursuing academia in whatever you do your masters in (i.e., Linguistics).
I think, potentially, a straight Arts degree might suit. THEN you get to make the choice between whether you want to pursue Law or whether you want to further your study in another field (linguistics etc.) This sort of leads me towards advising you to just do Arts at Melbourne if that's the campus you want to be at. I mean, what is it about the double degree that's particularly compelling to you, enough for you to be in this predicament?