Reading the info again i realized that it is too soon and we have too little info to really understand what they are trying to do with the new armory system. As someone stated before, i too now believe it is a spec system like WOW's talent tree and what other mmos are doing right now.

You play a conjurer and then you unlock White mage. You remain a conjurer but your Job is a white mage, meaning you get healing spells and buffs etc...

Just like in wow you can play a priest but you can specialize into healing or damage dealing(shadow priest)

I believe these jobs will be something resembling the talent trees in wow.