The most recent official message I've seen concerning DCM is a recommendation to avoid foods that contain peas (including pea protein, pea starch, etc.) in the top 10 ingredients. You (the OP) mentioned considering Blue Wilderness as a new food. A quick check of the ingredients of the Blue Wilderness Large Breed Puppy formula shows peas as 3 of the first 10 ingredients (they are 3 of the first 5 actually) ... aside from not trusting Blue Buffalo as a company, I would rule that food out immediately just by a quick glance at the ingredients.
I'm not a huge fan of Royal Canin, personally, but if it works for your dog then maybe stick with it. You could do much worse. If you do decide to change, I would echo a couple of other previous posters, and recommend you take a look at Victor's foods. They have a pretty broad line, including a few high protein, grain-inclusive foods if higher protein is what you are looking for.
Omen v Wolfstraum
Jasmine Katie v Doolanshaus