The closest thing that comes to a "witch" at the moment is elemental shaman. a class that can put curses (hexes) on enemies, use voodoo or other nefarious means to deal with their enemies, or use the power of tidal waves (sea witches) to deal damage to enemies. We've seen some examples of these individuals in the game: Naga Sea Witches, Troll Shadow Hunters, Hermits who are not shamans but are able to put curses on other individuals.
So in your opinion guys, can the lore support a witch class?