There is no reason for the hunter to just follow. The /assist makes the hunter attack. Others mentioned it, so I will too.
/cast [target=Charname-target, exists] !Auto Shot
/petattack [target=Charname-target, exists]

I wouldn't leave either without a target, or the alt or pet will pick their own. Not good. You might eventually get fancy and make the hunter always attack your pets target. Imagine a voidwalker tanking and you put the hunter and pet on void's target.
/cast [target=Charname-pet-target, exists] !Auto Shot
/petattack [target=Charname-pet-target, exists]

I can't imagine why, but you can do the reverse. Imagine that you want the hunter's pet to tank (tenacity pet). You send the pet and then you attack.
(on you)
/castsequence [target=Huntername-pet-target, exists] reset=combat/target , DPSAttack
(on hunter)
/cast [target=Mainame-target, combat] !Auto Shot
/petattack [target=Mainname-target]
The hunter's combat option makes him not shoot until the pet gets to the mob. The main's comma makes you not do anthing until the next time you push the button again (one push to send pet, next push to attack). This lets you do anything you want to any mob and still push your attack button and it automagically goes to the pet's target. No targeting needed. In other words, you can target a mob and still attack the pets target.

Hope that helps. Good luck.