A Dreamwalker and a wolf or wolfbrother have different abilities in T'A'R. A wolf is limited by their reliance on instinct - things that Egwene picked up easily from the Wise Ones, for example, couldn't really be taught by wolves. They can't teach Perrin how to create a nightmare, because it is hard for them to understand how humans think. You also see this when the battle started - the wolves just didn't have the ability to go toe to toe with Slayer, a Dreamwalker of limited skill, and he killed many of them with impunity. A Dreamwalker would be even more of a threat. Perhaps Perrin could learn from the Wise Ones, but with animals as his teachers, he will have different capabilities than Egwene will have. A simple example is that wolves think of manipulating the wolf dream using the same tools they have in the real world (they run, use their teeth to hunt, etc) - a human Dreamwalker, though, can accomplish things through willpower alone, plus they have human intelligence and creativity. So a human can imagine themselves becoming an animal, but a wolf can't do the same.