I don't see much wrong with this yearling's legs. They look like the legs of a growing Thoroughbred. A horse MUST toe out behind some (not point toes straight forward). The hind leg is a spiral and is constructed like a spring. If the hind toes point straight forward, the horse is bow legged behind at the hocks. The hind toes must point out a little to allow the stifle to clear the belly.
True Cow Hocks (which are impossible to tell from these photos) would actually angle IN at the hock.. like they were bent at the joint.
This horse looks like he might have a very pretty color when he is grown.. one of those black dappled horses with lighter brown at the flanks and underneath.