So I managed to answer my own question and resolve this issue, and like a proper user will gladly share my fix for anyone who runs into this similar problem.

Apparently as of OSX 10.7.2, Apple made some changes which will affect how you need to form your graphics EFI string / .plist file or it will no longer work with dual graphic cards.

Remove these lines for both graphic cards from your plist file:


and change the device_type for the first card to:


and the second card:

(this is only needed once per card, leave the "@0,device_type" style keys alone, only change the "pure" device_type.)

That's it! Now regenerate your EFI string using gfxutil or EFIStudio or whatever, pop it into your com.apple.boot.plist and away you go!