Yeh but even if the dispute is decided in hd's favour, I'm pretty sure the seller is required to refund only the cost of the item + the shipping to oz.
Return shipping will have to come out of HD's pocket and must be registered or express, which isn't cheap. Otherwise, without a tracking number to prove to paypal that the TM scourge has been sent back - they won't refund jack.
I think returning the item can be ruled out, so the best thing to do is continue communicating and further press your concerns that 15% is just not adequate. Knowing your picky ways HD, you won't rest until you get a minty TM scourge in that box

Maybe push for a 25% refund and pick up another figure on it's own on ebay?