If MM has a pet that can be a taunt bot perma then the specs balance in solo content is built around having a pet that can tank for you. So the base kit will always lack without a pet in solo content if it stays.
On top of that blizzard has a target key binds per spec so keeping the 4-5 keybinds required for MM to keep this taunt bot that will also decrease the likelyhood we will get new abilities to help us as a pure ranger spec.
IE the pet is holding back MM. The only way to keep the pet and keep it balanced is if it doesnt have a taunt\no micro management.