We are aware of the issues some users are experiencing with instances on the Retaliation Battlegroup, and are looking into the issue further. If you are experiencing these disconnection issues inside of instances, please post your ISP name and a tracerout here: Instance Disconnects – Retaliation 7/24

Details on how to perform a tracerout can be found here: http://us.blizzard.com/support/article.xml?locale=en_US&articleId=20628

We apologize for any inconvenience this may cause you and thank you for your patience and understanding while we work to get this resolved.