[Impaler]

I run an i5 2500k and a GTX 570, and I switch between CPU and GPU limited at the warpgate, so that combo is pretty even. In any battle, it becomes CPU limited. My brother has an i7 2700k and a GTX 670 and he's majority CPU limited all the time.

What I infer from the way the game performs is that it is not CPU or GPU limited, but memory bandwidth limited. This will still show up as CPU limited, so it's kinda hard to diagnose. One key symptom of this is the game being CPU bottlenecked while not fully stressing the cores - the cores are able to get the data out quicker than the memory bus can process it to the other components. A couple MMO engines I've played on previously (most notably Gamebryo: Warhammer Online & Rift) were notorious for being limited this way.

AMD's memory bandwidth is behind Intel's for the current generation by 20-30%, so an Intel processor will almost always run the game better than an AMD. A basic tree for performance (processor wise) would be:

Core 2 Duo/Quad = Phenom II = Llano
Trinity = Bulldozer FX = Nehalem (original i7s)
Piledriver FX
Sandy Bridge = Ivy Bridge

I think that better performance of the engine may be gained by using the fastest RAM clock speed & latency possible. I use 9-9-9 DDR3 @ 1600; at least in my case, I could go much higher.