As a hunter, the best thing if you're not a kid that cant control his fingers is to keep track humanoids on all the time and only shift to track hidden when you near his spawn points. Why? Because, for some reason, and I confirmed it on my druid also, both 70, he stealths only when you come to a distance of him. So he will first appear on track humanoids, or did most of the time, round 9 out of every 10 times I found him.
Still no mask in 20 kills but still, hope the track tip helps ;) Just bind the tracks to close buttons and change easily, thats how i did it. And once you learn his spawn points, you'll see its much easier that way.