MMO's are affected by graphics card--it's not just lag, or HD speed--for instance, the 128 bit bus of the Radeon 5770 can make a big difference vs the 256 of a 5850 regarding throwing large bitmap frames around, plus what impact does a 512 card have over a 1gig have when dealing with ultra high textures that newer MMOs offer? While, yes, the 3D capabilities will be ample for most of these cards, there's more to it than that. Anyone who says Internet lag is the only thing causing stuttering and hitching in a ultra-high textured DX11 capable MMO is not familiar with MMOs and their needs.
Challenging or not, MMOs are extremely popular, and game benchmarkers need to take them into account rather than just show us 20 different flavors of FPS games.
Just pick a popular, modern MMO and come up with a test and report the highest FPS running through the same zone at full settings with no discernible hitching, averaged. Not as standardized perhaps but there should be some nod to this gaming genre for people buying cards with them in mind.