Almondine is a great dog, no question about it, but I don’t necessarily think of her as "far superior" to the others. She embodies a certain kind of genius, as do Tinder and Baboo, for example. And, certainly, Essay. Each are distinct individuals, though, and I wouldn’t necessarily select any one of them as universally better than the others. What makes Almondine special in this story is that she has found her ideal match in the human world, and through her, readers see (I hope) what any of the dogs might be capable of.
As for your other point, it is true that Almondine was never bred. This reflects a writerly concern of mine—though I considered such a thing early on (specifically, that Almondine be the mother of Edgar’s litter) I didn’t think I could introduce that element into the story without diluting the relationship between Edgar and Almondine, which was all-important. I decided it would be sufficient for Almondine to be a sort of second mother to all the pups through the training.