Is Sylvanus rezzing Varian?

[Draeth]

AFAIK Sylvanas hasn't been shown to be capable of creating any form of undead herself, and her Val'kyr friends so far have only made run-of-the-mill Forsaken zombies for her. I don't see that changing any time soon, and there's not enough corpse left of him for that.

His soul wasn't destroyed by Gul'dan, though. Anduin has a nice chat with him during the Alliance-only Broken Shore quests.

The lil' bitches that got BTFO in their own class halls by the DK's?

Have you actually played the Death Knight order hall story? Because I have, and I seem to recall one of the Paladin's champions (albeit probably the canonical strongest one, Lady Liadrin) single-handedly punking the Deathlord, the three Horsemen who'd been raised at that point, and Darion, by herself.