Why does world of warcraft need to dowload 8.1 gb in patch?

So I bought the WoW battle chest today under the impression that I needed to just install and play the game. After installing the game and the expansion it then had to update from version 3.0.3 to 4.0.0. Next it had to go from 4.0.0 to 4.0.0.12911. Now its telling me it has to do some sort of Cataclysm patch (regardless of the fact that I don't own Cataclysm) which is a whopping 8.1 gb! Is this normal or can I just play the game. If its normal im pissed cuz it'll take now till christmas to download 8.1 gb through my at&t dsl. plz help.