Originally Posted by
Lokann
Dark shaman lore in its infant stages has been around since TBC, with some fel orcs having dark shaman NPCs and Ner'zhul in the Beyond the Dark Portal novel using some odd, dark shaman style spells, claiming he'd 'learned some new skills in the mean time'.
The lore class was revisited in Cata, first in The Shattering, where Thrall is forced to bully the spirit of fire into cooperation, and then as the shaman employed by the Twilight's Hammer.
The next appearance was when Garrosh employed dark shaman to strike against Northwatch in Tides of War, after that we had the dark shaman cult within Ragefire in the pre-MoP patch. Now, we're seeing the Kor'kron dark shaman.
It's an extension of the original lore, where a shaman had to ask the elements at all times. Now, this only applies to proper shaman, who actually understand that dark shamanism is destructive and highly dangerous, especially in a post-Cataclysm Azeroth.