ivy bridge motherboards and chips are different with lucid logix than the older sandy bridge, still may be crappy emulating the discrete card confusing cgminer. I have tried it without lucid installed and it does same exact behavior if i use both igpu and discrete.
i guess the dummy plug may be mandatory. i have a dsub and an hdmi switch on my monitor and tried using both connections on my pc to the same 1 monitor, but i cannot monitor the discrete temps and monitor the igpu at the same time yet device manager shows both devices fine. its just a matter of finding the communication port for the hardware monitoring when the igpu is being used at same time. not sure if its even possible.im sure if it was it would work.
i just plug into the discrete first ona fresh reboot, adjust the overclocks, then unplug it and plug into igpu and all works , but no hardware monitoring.