30 Seconds to Mars is a good band to sing about Northrend since their moody, somber feel highlights the questionable morality of everyone involved in the northern wars. The video seems to be very open to interpretation. It avoids giving a clear, inalienable message and instead sticks to presenting the audience with a series of genre flashes and montages throughout Northrend.
Medivh was an interesting choice to use as a singer for the song, but I actually think that it works out fairly well. He doesn't look quite like any other World of Warcraft character model, so stands a little apart from everyone. It's a good choice for a narrator, and I'd like to see Rogue Frog explore that in later videos.