australia post do NOT offer 'insurance' against breakages, so whether or not you had insurance would only insure against loss. never damage.

there is no 'fragile' service offered by aust post, so it is up to the seller to pack correctly.

you could take the vases and all the packing to the PO and ask their opinion, as for damaged items, where it is aust post fault, not the seller, and aust post think it was sufficiently packed they sometimes do offer compensation at their discretion.   However, this is something only the Buyer, and not the Seller has to instigate with Aust post.