GW2 is not as stable as TERA in terms of single-thread optimizations. GW2 exceeds at requiring you to get a good single-thread performance processor. (Mainly because TERA uses Unreal Engine, and GW2 uses a heavily modified GW1 engine.)

In GW2, this list: http://www.cpubenchmark.net/singleThread.html anything over 2000 will let you get semi-good FPS in Wv3 / Lion's Arch (Non-queue, overclocking (even if just +0.2 GHz) is highly recommended on anything lower than the 3770.)

My specs are in my signature on the lower image, and I can get severe lag in Guild Wars 2 in Lion's Arch, Wv3 and the bandit caves in queensdale (looking inward) My processor scores 1,271 on that list.

The only problem I have in TERA is the island with the rain cages. (Levels 32~38) FPS can drop all the way to 15~20 FPS.

The 3570k however will probably get pretty damn good fps on TERA alone, without OC'ing. GW2's just a "female dog"