Actually I don't see how Ghaz's Waagh is said to be bigger than Beasts' since I think Ork's armagedons' forces were said to number in 3-4 milions, which sounds really small compared to how many Orks Beast unleashed on hundreds of planets and what not, the book really makes you think like Beasts' Orks number in hundreds of bilions literally.
Then there's the fact Beast is far far far bigger than Ghaz, although we don't know who's the better leader since Beast hasn't made an appearance yet, in actual combat that is.
By the way, I was thinking, who do you think will kill Vangorich? The older fluff mentions him being killed by single surviving astartes, so I'm guessing " Slaughter " ? I doubt it's going to be some random astartes.
Also, any ideas on which temple Wire/Beast Krule belonged to? It doesn't seem like he was a part of the major ones, so maybe some unknown minor one?