If Tarby is not there, you'll need to wait for him to spawn (clocked at 15 minutes).
Speak with Tarby to begin a short ring event where three waves of wolves spawn and try to kill him.
Note: All group members must hail Tarby individually for their own quest-progression.
Important Note: When the wolves spawn, taunt or hit the wolves first. If they attack Tarby, he will fight them and LOCK the encounter. Even if you managed to tag the wolves without Tarby locking them, Tarby will still fight! Make sure none of the wolves are targeting (and thus fighting) Tarby. He has very few hit points and will die quickly. If he goes down at any point, you must wait 15 minutes for his respawn.
A good strategy is to pull the mobs away from Tarby so nothing gets close enough for him to attack.
Once the wolves are defeated, hail Tarby (have all members time your hails so you don't have to wait for Tarby to respawn) and pick him up.