I have new 2012 servers and so far its only set to allow administrator to remote in.
In Computer Management/Remote Desktop Users, the only member is administrator.
When I try to add the built-in Remote Desktop Users group from the DC, the server does not see this group.
Best Answer
The builtin group that you are referencing allows users to log in locally to domain controllers. That is not where you want to add your users. https://technet.microsoft.com/en-us/library/cc756898%28v=ws.10%29.aspx
What you want to do is create a new security group and use Group Policy to propagate that group to the Remote Desktop Users group on local servers
http://social.technet.microsoft.com/wiki/contents/articles/17671.how-to-add-domain-usersgroup-to-remote-desktop-users-group-on-servers-using-group-policy.aspx