Luckily for me, the Daizyujin never showed up in the NES game whilst translating it. It would have been a nightmare. It's bad enough getting the character names to sound semi-English.
But, you're asking for a localization, rather than a translation, right? I think that "Great Divine Beast" doesn't work very well, because you're implying that it's a Divine Beast rather than a God of the Great Beasts, or whatever. When I see "Daizyujin", I think Great Beast God, viewing the 'Jin' as a noun, rather than an adjective. Maybe approach it from that angle? Of all of the great beasts, (if you're going with 'dino ranger', then maybe dinosaurs), this is the ruler/master of them all. He puts them all to shame, etc.