Call me dense, but I didn't realize until recently just how darn useful this spell really is.
Unlike Polychromatic Rune or our Epic 1.5/2.0 clicky, this Rune does not trigger on fade. As long as the Rune is on you, anything hitting you has a VERY high chance of triggering a -400 Hate reduction effect.
Now, for higher end encounters, it'll probably be gone in a single hit. For everything else, however, the more it hits you the lower you go on the Hate list. Eventually, the mob's going to decide to go play with someone else.
I noticed this tonight while raiding Vishimtar the Fallen. A bunch of skellies were running around, ganking people left and right. A couple of them started playing patty-cake with me but, by the time they'd gotten through my Runes, they were running off to find another "friend". This gave me ample opportunity to make it to safety.
(I do apologize to the Ranger who was next on the Hate list; but better you than me!)