Hi,
After running WildStar (a game) for the first time I noticed that it does not use my NVIDIA card either.
What WildStar and UE4 have in common is that they are both 64-bit programs. So I figured my NVIDIA Optimus implementation might not work properly for 64-bit programs.
To confirm this I have compiled my own 32 and 64 bit programs that use OpenGL and saw that the 32-bit program uses my NVIDIA card and the 64-bit program does not.
According to this, the problem might not be with UE4 but with my laptop…