Most compounds unload the rotor to a degree in high speed flight. In the X3 case I imagine the lift at speed comes from the stub wings and fuselage, and probably less from the articulated rotor in autorotative cruise.
However if the mast could tilt and the rotor was of sufficiently high inertia to reduce Nr and approach efficient Mu values, it could conceivably fly like the cartercopter...though this would likely mandate a main rotor design which, like the CC, is not very efficient in hover.