Your example of collie herding behavior is cool; I'm not sure what to make of that. Do wolves herd their pups? Or are there other plausible precedents? How complicated is collie "herding" behavior?

As to smell and tracking ability in blood hounds: given that these same abilities occur in wolves (though to a lesser extent?), my guess would be that these adaptations are relatively simple to acquire, if you have a wolf's genome as your starting point. Designing smell for the first time would be complicated, but designing a better sense of smell from a wolf's sense of smell might just require sending more brain cells to the "process smells" brain center, or building more of the kinds of olfactory receptors dogs already have, or some other simple shift. (OTOH, if blood hounds are sensitive to many compounds that wolves aren't sensitive to, or if they exhibit many strategies in tracking that wolves don't exhibit, I'd be wrong and surprised. Let me know if that's so.)