Hunters aren’t casters, so not really a good comparison. Everyone is saying DKs fill the niche, which I don’t agree with. If they don’t want to add the class, the glyph is the easiest option and makes the most sense for the minion spawning aspect that a necromancer might do.
And isn’t demo more of a shadow spec than fel? I haven’t played it in a bit but I don’t recall them using much fel.