Innovation in game mechanics are more necessary than facilitating a new style to the hotbar. Consider how non-mmo RPGs continue to sell with the controller- different game mechanics separate each title. Before you counter my point that single player RPGs do offer great storytelling let me remind you that does not make it a game- such is the reason why World of Warcraft has such great replay value: Differentiating gameplay through new (to the player) classes, and new content.

I compare most of my MMO's that involve a hotbar to Anarchy Online, then SWG, THEN World of Warcraft. Wow's balanced game mechanics will never compare to AO's overpowered classes that counter eachother, balance tipped into the direction of the player with more knowledge of character "twinking" (at all levels, including maximum level) the latter includes pvp and pve.

The reason why most compare MMO's to World of Warcraft is because of Wow Tourism, the idea that they are amongst the seemingly 8 million people who started playing MMO's by hopping on the World of Warcraft train, and what a train it is, that train is even more packed than one in Japan!