Is Revelation the ultimate deus ex machina?

Yes, but let's not be too critical of the author. He was, after all, tortured (according to legend with boiling oil), and was exiled to a prison camp on the isle of Crete. Suffering from PTSD and more than likely physical ailments, we can only feel sorry for him. The rants he makes in that book are evidence that he was escaping reality for something better.