I'm not sure how they managed to get NRT > SGN > MEL to price out at 90K in J - I was able to find HND > SGN > MEL at 60K in J on a random date (May 16):
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That being said, if I was them (and I'm not them by the way), I'd try to force a routing where you fly ANA from Tokyo down to Sydney then connect onwards from there to Melbourne with Virgin since Virgin is a partner of Aeroplan and generally makes business class available too! I'd much rather be stranded in Sydney than Saigon!
As an alternative, if you do get pushed into that upper bracket of 7,001+ miles why not make the most of it by adding on a stopover in Melbourne instead for an extra 5000 points? From there you can fly pretty much anywhere in the region in business class be it on
Virgin Australia or Air New Zealand (i.e. you can make your way over to Auckland in J at a later date!)
-RooFlyer88