With Optimus you cannot disable the iGPU in bios. You cannot uninstall the iGPU drivers either. In the nvidea control pannel you must force DayZ to run with main card, but just doing this does not activate the card. I have tried pretty much evey option, I am now waiting for an updated driver from nvidea or DayZ update that could fix the issue. Honestly I think optimus technology is load of bull, the advantage of having a longer battery life when unplugged does not out weigh the hassle that you get with just about any game or program.

I have had the same issue, around september 2014 I scoured the internet for a month to find a fix with little luck. The only way I could get it to switch from the integrated graphics was to reinstall the Nvidea drivers everytime I turned my notebook on, install nvidea inspector to see when the GPU is kicking in. Extremely frustrating. Have you found any other solutions?