Following on from the well documented issues with Essentials era servers and the 'magic' it does to allow the server to be on a dynamic IP address (that being the Windows Server LAN Configuration Service) Microsoft released an Update Rollup that included some new tweaks you can make to prevent these changes.

I blogged about Client DNS back in June 2013,  i also wrote this script but never got around to pushing it out.

You can run the script on an individual client, or you can run it on the Server to have it apply to all clients.

Official Documentation: http://support.microsoft.com/kb/2862551/en-us

This should also work with Essentials 2012 R2.