No, he doesn't. Because these a multiclasser wizards, who use guns. Because Wizards run out of spells. Besides, they're too cool for Gandalf and Dumbledore. A Warlock Guardian could do some major damage to Death Eaters, and I KNOW they would kick the ass of any Orc.
well we don't know if the Vanguard will be an actual class.
As for the Cabal? here's what I know so far: They are found on Mars They are broken down into ranks, so there are of various sizes, but still very broad. They use dropships similar to the phantom from Halo.