The times I've seen nofier around the parth farm, he's always acted in a specific pattern. He'll walk in a straight line towards the parth farm. Both times, somebody in my party attacked it with his pet to pull it. The pet dies instantly, and the nofier turns around and begins making a beeline straight for the tower at the entrance to Bri Leith, where it gets horribly slaughtered. It doesn't slow down for anything. Definitely a quest creature.
And to whoever said that there should be something immune to melee, that would be a REALLY bad idea. Without any way for tanks to hold it off, the creature would slaughter any archers and casters that attacked it.