Matt Thomason
Hero
I am not sure what you would be suing WotC over in that case, sending a fraudulent C&D ? Is that a thing? To me the next move after not agreeing to the C&D is on WotC.
Either way, the way to a copyright infringement case goes through proving 1.0a is revoked
I have no idea about how you can actually legally respond to a C&D that says the sender has rights they don't actually have, so I've put it as a possibility rather than a certainty

I would imagine there must be some legal backlash to a C&D that has no weight, or we'd all be sending them to everyone all the time... (wait, was I supposed to be sending them? Nobody told me!!!)
At the very least, however, in this specific case I would think likely sue for breach of contract due to them not following the terms of the 1.0a license that requires them to give you notification and 30 days to fix. Whether you would win is another matter, and depends of course on whether that 1.0a license is still valid and authorized. It looks like whatever possible route is taken, it has to come back to that.