There are allot of WOTLK servers because WOTLK was the most "popular" patch of WoW and allot of work on both the emulation and the database was done for that patch.
However private servers for Cata, MoP, and WoD came out pretty much almost hand in hand with live release, they were and still are utterly garbage but most private servers are.
This is quite big it's the first time for quite a long while that Blizzard went to close an private server, and it's the first time that the server in question was not hosted in the US/CA and was not anywhere close to emulating retail content.
The content that is available on Nostralius is literally not available on any live server any more since Cataclysm which altered all the original "vanilla" content.
This might actually also be interesting to see if this can actually go to court, the server emulation (if done as a clean room) does not infringe on Blizzards actual IP, all the text, sounds, textures models are present on the client side alone the server holds only an itemized database of objects and knows how to communicate with the client.