Kaveri runs bf4 at high and ultra here at 720:
http://www.youtube.com/watch?v=axyHkKn_e80
Now add mantle that lessens the cpu load and it will walk all over a dual core i5 in multiplayer. Whatever the gfx attached.
Now my gaming notebook is loaded with quad core i7 so i am not nervous. But if i had a dual core i5 with a nv card. Man ohh man... Thats not working for the new performance games.
Because a bunch of guys playing on a random computer is suddenly legit? I don't see a CPU-Z shot anywhere and this video could easily be faked to get views.
You are also forgetting that on laptops the GPU takes the vast majority of the hit in the conversion to mobile. Simply put mantle isn't as awesome because the GPU is limiting the settings to begin with. A 650m is mediocre at best when compared to desktop cards. For a SV i5 haswell (say boost to 3.2 ghz which is expected) its like pairing an i3 on the desktop with SUB 650 (desktop) performance. In the vast majority of cases the CPU will not be the limiting factor. You will be lucky to get 1080p medium 40-50 fps on a 650m, at that level the i5 CPU is fine.
Don't get me wrong, there are some games that are CPU limited (mainly Gw2 for me) but not many, especially when we are talking integrated level of graphics.
Mantle very well may walk over it but nothing at this point in time makes that statement likely.