These Minecraft builds do use game mods or third-party tools, and there are blocks incorporated into the designs that cannot be placed by players (such as the blocks of Coal in Deathwing) -- but cool is cool, regardless of how something is made. Many viewers of the Ragnaros video have commented that he looks a bit ... green. However, kattooMC assured everyone it was just a result of video encoding. As a Minecraft player myself, I'll back him up on that. I know what yellow wool blocks look like when I see 'em.
According to kattoo via Twitter, Stormwind is next on their Warcraft to-do list. I, for one, can't wait to see it.