I've noticed something. All expansion packs feature final bosses from the original Warcraft series. With Deathwing revealed, that makes 3 for 3. According to the scientific method, a minimum of three trials must be made for it to be proven. Therefor, it's now been scientifically proven that Blizzard is being unoriginal with their expansion pack characters. What is the WoW Community to do about it?

Ask for more :)

Technically they are following the story line if you have read any of the books. Deathwing has been in hiding ever since he lost the dragon soul aka demon soul. After the other dragons got there powers back. The old gods have been nagging at him for years and he finally come out to play.