You're getting a bit carried away... they might be able to, but there are battles in the Campaigns where they would be completely wiped out. The Archangels, with their Divine Retribution ability, will send them flying into the clouds while the vampires take care of the rest. In my opinion, the most useful unit in the game is the Mummy... I carried around almost a dozen of them for most of the game. They were very helpful in preventing me from losing troops.
The God unit isn't that scary. You just stand there and resurrect vampires with Liches + Mummies + the hero, until their maximum HP is less than 20, and even better, bring it down to 1, and then any attack on any unit will fully heal the vampires. (And you can also just kill the Angels first, haha).
I disagree about the Elrath's Avatar. In the last mission, I just one-shotted it with vampires. I had so many of them there. But I'm just a hardcore player; every battle is a new week of Dark Energy.
Also, I agree about the voice acting. I think I heard that there are 3 people helping with the voice acting, but even if the author wants to update the voice acting, it will take another month, or even longer.