Yahoo uses akamai technology (bgp path analysis) to determine what content server is “closest” to a given host and bases its’ dns response on that data. You could contact Akamai and, explain your network, and see if they can make the necessary adjustments, or if you are large enough ask them to drop a couple of servers in your site. (or they may want you to send them a BGP feed)
But we are happy to work with you to make things faster / better.
Any particular reason you have a problem with multiple answers? We do it intentionally for several reasons (e.g. load balancing and redundancy). It is fully RFC compliant and has been working well for many years now on most of the large web sites on the Internet.
