Tier 1 will help you to keep a decent attack speed to poke.
Tier 2 Greymane need a lot of mana to keep the poke on lane.
Tier 3 is a good Human poke to keep yourself safe while your mana is low or even you lane is pushed.
Tier 4 ALWAYS!
Tier 5 You are the hunter here, not the hunted, so run like a real wolf and hunt them dowm!
Tier 6 More damage against Heroes is always welcome.
Tier 7 or both are good, the choose depend on what form do you like to keep pushing and hunting.

Lane Push and Poke
Human: Use to push and poke enemie wave and Heroes, keep your active, Human is the best option to push.
Worgen: As Worgen you have a good disengage with your E rolling back but you will be exposed everytime, use Worgen Form if your enemie is pushing hard and you need the extra damage to push them back.

Use > > Leap > > AA and then run or E back to your spot.