I'm currently playing on a private server called Firestorm Servers, they have their own custom website and also a launcher.
This launcher is very use to use and you can easily download 4 different expansions which I've listed below:
- Wrath of the Lich King (Patch: 3.3.5)
- Cataclysm (Patch: 4.3.4)
- Mists of Pandaria (Patch: 5.4.8)
- Warlords of Draenor (Patch: 6.2.3)
It's an user friendly launcher, I'm not entirely sure if you still have to create a account but that's not a big deal.
If you have to create a account just do it and download the expansion you are willing to use it will take 2 - 5 minutes to download.
The download speed is depending on how fast your internet is going, for me it took 6 minutes to download Warlords of Draenor.