So just because previous movies about previous games weren't blockbusters, that means that it's impossible? That's some logic for ya. This is Blizzard. This is Legendary. They are putting a lot of work into this, they aren't rushing it. It has a good chance to be a good movie. It may not be the best WoW movie imaginable, but it has a good chance at being at least a decent movie.
To say you know it's going to be bad is just silly. There is barely any information on it at all.
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Good theory, too bad they already said that characters we know will be very active participants in the movie.