Are you 100% sure it's ONLY on Rdc? I mean, if you plug up a local monitor/mouse does it not drag? Ive been working with Martin to optimize the GUI's CPU usesge on Windows. It's the only VI I own that Shows any increase in CPU usesge just displaying on screen--minimize it, the CPU usesge goes away.
RDC is using a special terminal services video driver...thus, I would think its related. If the GUI hits the host CPU hard, having a terminal session convert it to that transport is going to be even harder on the system.
I really wish they would gut the GUI and start fresh with an API call based, reSizable win32 GUI. The Instrument itself is magical, and SUPER CPU efficient. The GUI is a resource hog--albeit a bit less of one with the latest beta build. Still, why it uses so much CPU where bfd2, Kontakt, B4, Atmosphere, and any other doesn't use any noticeable CPU time, is a significant issue. When your GUI takes more than the sample/synth/filter/reverb/pitch dsp, that's an issue.
Does it change if you reduce the color depth of the Rdc session?