If you're determined to do this anyway, it's probably best you get the angels right. Given they're more or less the iconic emblem of shit going down in the Old testament, make sure you get them intimidating as fruck and very much serious business. The funny thing is the more biblically-accurate you make your angels, the less likely they'll be noted.
First up, an angel is serious business. Not just serious business, but OH MY FUCK SHIT'S GOING DOWN serious business. If an angel shows up, eve nif its intentions are not hostile towards you, it means that somewhere nearby, something apocalyptic is going to happen. In all the biblical history of thousands of years, angels only showed up a few times, and every time they did, something absolutely massive happened. This is one of the reasons so many people's reactions to the visitation of angels was to immediately fall to their knees and pray like never before; they knew that almost everyone who saw an angel saw it coming for them, that there is absolutely nothing they can do to stop it, so they might as well pray before they die.
Secondly, angels are so powerful it boggles the mind. Not just a little bit, but sanity-challenging in the shit they can accomplish. If I recall offhand, there was once an army of about 65000 abyssinians ,who had absolutely wreckjed the shit out of everythign that came close to them, and that were a few kilometres from utterly destroying the Jewish people entirely. They were battle-hardened, very well-led, and generally one of the most powerful military forces assembled in that area ever.
One angel killed every single one of them in one night. That's two-and-a-quarter people EVERY SECOND, not including the time it took to move group-to-group or chase fleeing ones. You shouldn't have the players challenge one of these at all until the climax of the game, and even then, after a huge amount of power-gathering and elaborate planning to weaken it before attacking.