I suspect it could just be the craptastic benchmarking on that site, the other big option is that it's a memory bandwith issue. Remember, the 2 Bobcat cores and that monster of an IGP are all sharing a single channel memory link. It's possible that the stronger CPU is taking up more of that link than the Atom is.
Also, remember that the GPU in there is stil a 5XXX series design using VLIW5. AMD has admitted that with VLIW5 they were seeing something like 65% usage of the theoretical GFLOPS in real life scenerios. And, despite improvements, WoW still favors Nvidia hardware.
Just to note, Memory bandwith limitations can be very severe on IGPs. With my netbook, there are some games where switching between the stock 400mhz GPU speed and my 700mhz OC doesn't do much of anything, and I've got 800mhz DDR2 in dual channel. (Civ5, I'm looking at you)