The reason why they released a token for WoD and not for Pandaria is because those things show completely different things. Having the WoD weapon skins is a show that you're just generally good enough to do the challenge mode dungeons, but it was BS and annoying that if you did those on a Warrior vs a Monk you had access to way more skins simply by class choice even though the weapons themselves were pointless. That's why they added the token.

The Mists challenge mode appearances showed you were good enough to get those things done with your class. That you were good enough at Warrior to get the dungeons done. But if you sucked at Monk and couldn't do it on one, or didn't even have a Monk at the time, why would you be able to get the challenge mode for Monk? You weren't good enough/didn't put in the time/didn't even have a monk for Mists Challenge Mode so it doesn't make sense to be rewarded with something so specific to that class.

It's like the Mage Tower Challenge skin. Sure you had enough mastery of your class to do it on a Warrior tank, does that mean that you should auto-unlock every other tank spec skin? No because each of them require different skills and just because you did it on one doesn't mean you can do it on another, even at equal gear. Take it from someone with the BrM and WW mage tower challenge skins who would love the ability to get the sets again, it's a badge of being skilled enough at the time on your class to get those things done, and just because you did it on one class, doesn't mean you could have done it on all of them.