I share your pain, I have an ativ book 8 with 8700m and intel graphics.
newer games all run great, older games run awful. I think that is a combo of the gpu setup and windows 8 because my older samsung laptop with a less powerful nvidia gpu and windows 7 could run anything I threw at it to at least medium graphics. (By older I am talking 1 year older tops)
I have updated to windows 8.1 and updated all drivers and software through samsung sw update, tried to update the gpu again through amd site, but when I select my graphics card and try to update...I am told there was no compatible hardware detected. When I try to change any settings in catalyst I only can see the intel graphics, or when I try change settings in older games like deus ex I am also only shows the intel graphics as well.
I have not found any solution to this problem, and maybe it is not a problem and you are only supposed to see the intel graphics in programs and it is more of a windows 8 issue...
I cannot share more than that right now. I plan to keep searching for whatever way I can possible get everything to run consistent on this machine and I will share any progress with you if I manage to find it.