Speco,
Thank you for the guide, I am curious though as it appears to be out of date.
Having acquired the severed Head of Nefarian players are thus unable to enter Black Temple.
Could it be that, one must complete the Shadowmoon Valley quest chain beginning with (wowhead.com/quest=10568/tablets-of-baari) Tablets of Baa'ri to gain entrance to the Black Temple?