World of Warcraft: Hunters! Why isn't Marksmanship working for me?

marksman really isnt that great at the low mid levels, it excels when you can max the tree. Your pets not holding aggro because your outdamaging it, before when you were BM your pet was a beter tank and dealt more damage. Now it has harder times tanking due to being worse and even if it growls everytime the cool down is up your gonna keep pulling aggro.