The latest Warlords of Draenor
beta build includes the following item: Corrupted Blood of Teron'gor
. Spoiler alert: that's the orcish name of Teron Gorefiend, everyone's favorite pre-Scourge death knight. The means of acquisition is unknown, as is the end product.
Given Teron Gorefiend's history, the legendary will most likely be caster-centric, unless Blizzard goes the road of the legendary cloak and provides something for everyone.