Nathanos and Moira have been around since Vanilla WoW. But they've, Nathanos specially, have only been used in the plot recently
Yeah, I'm leaning more towards the idea of Alleria being understanding of what Sylvanas has done rather than be accepting or approving of it. I mean, the way I see it, Sylvanas does the things she has to do to protect her Kingdom and people, be it Quel'Thalas and High/Blood Elves or Undercity and the Forsaken. She never asked to become the Banshee Queen, though she has done some fairly questionable(see fucked up) actions as of late, but she wasn't responsible for mass-scale atrocities like Wrathgate(right?) and Theramore.