And could I then dispute the chargeback with my credit card company or am I wasting my time?
No, I'm afraid you can no longer dispute the claim with the credit card company. This is because under eBay's (newish) managed payments system the buyer pays eBay, not the seller.
Previously, the chargeback would have been issued against you personally, and you would have had a right to challenge the case and, in the last resort, to appeal to the financial ombudsman. All these rights have been removed from the seller (whilst the buyer still retains them).
I raised this concern with eBay several times when I was an invited member of their Managed Payments Advisory Group, but as they never replied I left the Group.
Now, chargebacks are issued against eBay itself. There is little chance that eBay will contest it and the user agreement requires you to repay them for the sum charged back (they will also charge you for doing this). And with no certainty that your item will even be returned to you.
eBay does indemnify sellers against chargebacks in some situations, but only those which claim an item was never received, or that the buyer didn't authorise the payment. But not where the buyer claims th eitem was not as described.
If it's any consolation, it would have been much the same if the buyer had opened a case under eBay's money back guarantee. eBay's attitude in these cases too is that it doesn't see the item concerned and is "unable to determine who has the valid case, or take sides". Unfortunately, eBay's idea of not taking sides is to find in the buyer's davour, and require them to refund the buyer.
eBay has become a seriously risky place to sell things.
