WoWDB

This enchant illusion is not usable by hunters, probably because their class weapons are bows, crossbows, and guns.

Edit: It's now back in the game. It is sometimes available from the Black Market Auction House, like  Core Hound Chain.

It is now also possible to loot it from  Smokywood Pastures Special Gift.

It is. (source)

As of Patch 7.0.3, you can finally use the enchant illusion account-wide! :D