SMAA is better than FXAA and whatever ones this game uses, and it doesn't take much performance hit like the other AA options.
http://mrhaandi.blogspot.com/p/injectsmaa.html
I wouldnt use it, especially since they have been ban happy lately. their response on SMAA injector
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The use of third party program of any kind is neither encouraged or supported by the Guild Wars Support Team. Based on the information provided, while the purpose behind use of the third party program seems to be rather benign, the method by which it accomplishes its goal may subject your account to action.