Since Exchange 2010 SP1, you can enable DAC mode (Datacenter Activation Coordination) even if you have a DAG on a single AD site. Lots of people are not aware that DAC mode not only helps preventing split brain scenario using a smart and simple mechanism (“hello I’m there and I’ve mounted databases” bit, and boot times), but also add 3 commandlets to make DR switchover / failover easier !
Note: This is also valid for Echange 2013
More info about DAC mode, check the differences, not so much different from Exchange 2010 SP1 to Exchange 2013 – YaY, less new things to learn !