I have an OpenID relying party setup and using XRDS. It passes the \"RP has discoverable return_to\" interop test over at http://test-id.org/RP/DiscoverableReturnTo.aspx.
Maybe it's just a cached response from AOL and tomorrow it goes away. Just a thought. The test-id.org test and Yahoo test you've already done should demonstrate you're doing it right.
Please let us know if there's a novel requirement AOL holds you to that others don't.