I don't believe DNS supports regex and in fact a comment thread from 2010 on OpenDNS specifically states they do not support it [1]. A very simple solution for this is a load balancer. Nginx [2] works quite well and routing is a breeze. The downside is maintaining the instance on which all of your traffic flows. You'll likely need a hotswappable fail over hosted in a different data center to be safe.

[1] - https://forums.opendns.com/comments.php?DiscussionID=8440 [2] - http://wiki.nginx.org/Main