Yes but you can get in, and you will eventually get in, the theatre is only temporarily oversold, and you can come back and watch the show in a day or so when they have more tickets and you get your moneys worth.
There is nothing they could do about the servers, it's not Blizzards fault, especially with that amount of people. If you saw a theatre with 7 million or so people all going in at once, i'm sure you'd have some sympathy to the theatre company, and still they manage to provide you with what you paid for with little downtime.
When you buy games that require a maintained internet connection, you shoud be prepared for server downtimes/repairs, anyone who whines about these problems and demand their money back don't deserve to play the game.