I could be wrong, but I heard the best diet for the majority of dogs is 60% protein, 20% veggies, and 20% starch (pasta, rice, potatoes, etc.). I probably read it on one of your guys' WP blogs, so fucked if I know if it's true, but it's what I go by.
I think it's probably more like 60% protein 35% fat and 5% greens. A dog isn't going to process corn and make it into bread to eat. And dogs and predators don't eat vegetables unless it's some grass to help their digestion. Humans can also live well on a high fat diet with very little vegetables. Inuits do so and they generally have less heart disease. I would think it would be important to get grass fed meat though.