What does it do exactly? Does it simply make the boss attack somebody else or does it make the monster stop attacking and go away? Is it something I should have? Thanks :)
Kami's Forgiveness resets monster(s)' aggression. That means if you stand there while healing other teammates, not all monsters around will target you due heal. Else if you get attacked but you see that you wont make it, you can reset agro of monsters and escape.
In my opinion you should keep an eye on damage and healing. This skill lasts only for a short time, you have to rebuff you all the time. It proves a disappointing choice during a fight.