On a serious note, how many rpg games let you play out the anti-hero roles?
Despite their description as RPGs, most MMOs don't really have any role playing beyond what you bring to the table. In SWTOR, for example, you do have the ability to choose light side/dark side in many conversation situations, allowing you perceive yourself as an anti-hero, but the practical effect is limited at best. There's no real in-game effect to your choices, so it mainly comes down to how you want to perceive your character (and whether you want to power-game the stats).
City of Villains allowed you to play as a villain, but not really as an anti-hero.
I'm not sure the structure of MMOs would really support that as an option, without making some fundamental changes to how the game(s) played out.