Yes, all-meat diets are NOT balanced. You cannot feed a diet of just meat to your dog and expect it to do well. Your dog needs bones and organ meat as well to obtain the proper nutrients. This means feeding a prey-model diet based on a whole prey animal. Remember that your dog has no needs for vegetables, and that most of the nutrients in vegetables—even pre-processed ones—are unavailable to your dog (see the omnivore myth and the stomach contents myth for further reference). The alternative? Feed according to the prey model and provide variety. If you are feeding whole animals or a variety of raw meaty bones and organ meats, then your diet will be balanced. Raw foods contain the exact proportions of fat, protein, vitamins, minerals, and enzymes a dog needs.
One other concept of balance that should be addressed is the idea perpetuated by the pet food companies: "Dogs need complete and balanced nutrition in every meal." This is nothing but propaganda designed to make people buy into commercial dog food. This is not how the canine body—or any other body—operates! Take your own diet, for example. Do you eat a complete and balanced meal every time you eat? No! You eat a variety of foods over a period of time, and yet your body generally does very well and exhibits no signs of nutritional deficiencies. Dogs do not need "complete and balanced" nutrition at every meal. If they did, then any time they did not receive complete and balanced nutrition their bodies would get out of skew and problems would suddenly develop. This is not how it works. This is where one sees the concept of "balance over time" developing. This is the principle that many feel is adequate to explain how all living things obtain the proper nutrition. Nutritional needs are met over a period of time, and balance is achieved through time as the animal eats what it needs at the time it needs it or whenever it can get it. The nutrients the body MUST have and cannot synthesize for itself are supplied in sufficient amounts in the food the animal eats. Nutrients are stored within the body when they are eaten and are not needed, but when the need arises, they are essentially pulled out of storage and used. This is what allows animals (and people!) to fast for sufficient periods of time without starving or dying. They not only have fat reserves and protein reserves in their muscles, but stored up nutrients and vitamins in their tissues (fat soluble vitamins, for example, like A, D, and K).
One can logically ask: 'What is balance, anyway?' Balanced vitamins and minerals, carbohydrates, fats, and proteins? Can we ever conclusively know what balance is? How? No, this concept of balance is a myth. We hypothesize, guess, and draw up faulty food pyramids in attempts to define 'balanced' diets, yet as a society we are still plagued with obesity, diabetes, heart disease, and 'rare' bowel diseases like Crohn's disease that are becoming more commonplace (oddly enough, vets are seeing the same things occurring in our canine and feline counterparts). The food pyramid is being revamped as specialists argue about appropriate 'balanced' diets, which only further illustrates the truth that we do not know what balance is.
What about our pets? The standards for balanced pet food are approximated (and incorrect, I might add, since they are based on the myth that a dog is an omnivore. See the standards myth for more detail), and vitamins and minerals are added in excess to compensate for the decreased bioavailability of these nutrients in kibble. Dogs are fed "balanced" proportions of fats, proteins, and the carbohydrates that they have no need for whatsoever. Honestly, have you ever heard of an essential carbohydrate? There are essential fats, essential amino acids (obtained from protein), but no essential carbohydrates. Yes, an animal's body needs glucose to function, but glucose is easily made from amino acids via gluconeogenesis. Carbs are not necessary for our carnivorous pets, yet they are listed as part of a 'balanced' diet. For further discussion on carbohydrates, please visit the Carbohydrates page.
We can go one step further with this concept of balance. No one except nature conclusively knows exactly what is needed and in what proportions. Why? Well, a million years of evolution should be sufficient enough to show any naysayer that the diet nature provides for her creatures is precisely what they need to function, thrive, and survive. No one but nature knows exactly what the animal can actually use and absorb. We can only guess. So forget 'balance' of any kind when it comes to feeding our pet carnivores. There is no such thing as 'balance'. Think "carcass". "Carcass" is what sufficiently sustains wolves, dogs, wild cats, and ferrets, and that is what nature has perfectly provided for them. "Balance" is nothing but an insufficient human term, a vague concept that pet food companies employ to make people buy the foods for their pets. When feeding your pet carnivores, always remember the concept of "carcass".