Isnt Necromancer and undead more of Gridania's stick? I mean, there are cases of undead everywhere, but undead and dark magic in generally has a centrally heavy theme in the shroud and gridania in general.

If I am following what the Dev's have announced, they said they will be adding two new jobs and classes. One healer and one tank. possibly more than that though. The 3.0 build will have a heavy theme on Ishgard in general so its safe to say the a class like Dark knight will be given. Templar seems to be out of the question though because we have Paladin's and thats what Templar's are, just with another name. I think the Ishgard pope and his clergy could have some interesting lore as cleric's and healers so realistically, we could see Dark Knight and Cleric=>Bishop.

Dark knight might also get it's own base class if it doesn't share the same weapon set as Paladin.