Is this limited only to the Real-Time Process Explorer? Are you able to monitor processes on these servers that are monitored as part of any of our out-of-the-box application templates, such as the Windows Server 2003-2012 Services and Counters template? Also, have you tried using the "Component Monitor Wizard" to browse for Processes running on those hosts?
I just checked my lab and I'm not able to reproduce this error against my Windows 2012 R2 Data Center host. Please also verify that the node is managed in Orion using WMI, and that the credentials used have local administrator permissions on the monitored host.