It is too soon to pass any sort of ultimate judgement, but I don't think it's a stretch to imagine the Mists of Pandaria "Legendaries" are going to feel much more common. If that is the case, then... what actually makes these weapons "Legendary", at all?
I know a lot of people like to bitch about things being "flavor of the month", but honestly, isn't the sort of the point of Legendary weapons? To cast the spotlight on a specific role in combat, not only to give them a feeling of satisfaction and achievement, but to also inspire others to consider pursuing that role? They're already handing "Legendary" items out like candy, as per the quest-chain. It doesn't make you feel cooler; it makes Legendaries feel trivial.
I normally refrain from casting sweeping judgments when it comes to game-design, but this seems like it was really poorly thought-out, and they're pretty much ensuring that nobody will ever few this new "Legendary Tier of weapons" with any degree of respect, admiration, or status. In short, they will be generic stat-sticks, no different than every single Epic in the game at the time of its release.