While the reports of DCM are worrying, I think it is important to remember that they are still a tiny number, compared to the thousands of dogs eating these foods. Grain free was always a bit of a fad, in my opinion - grains have a long history of safe use in dog food, so unless your dog is intolerant there is not much point in avoiding them, especially given the correlation between large quantities of legumes and potatoes (used instead of grains in commercial foods) and an apparent increased incidence of DCM.
I do believe that there is benefit in feeding a range of different foods - that way a possible excess or inadequacy in one is balanced by the others. If you have concerns talk to your vet, but don't get overly stressed - there are people who will assure you that grains are killing your dog, that raw meat will lead to horrible illnesses, that cooking meat destroys its vital spirit, that all dogs should be vegan for the sake of the planet, that dogs should eat nothing but meat and bones, and that no one except a fully qualified dog nutritionist can possibly prepare a properly balanced diet, but most dogs live long and healthy lives, eating a very wide range of foods. I would simply buy a good quality, meat based complete food that your dog likes and you can afford, or do the necessary research and prepare one at home.
