The latest August 2014 update rollup for Windows Server 2012 R2 has addressed this issue. The integration feature previous only worked when the Essentials server was the only domain controller in the domain, which led to some difficult workarounds in migration scenarios.
The rollup can be downloaded via Windows Update or directly here – http://support.microsoft.com/kb/2975719.
You can read the Microsoft announcement here – http://blogs.technet.com/b/sbs/archive/2014/08/13/announcing-the-availability-of-enabling-windows-server-2012-r2-essentials-integration-of-microsoft-online-services-in-environments-with-multiple-domain-controllers.aspx.
