The Spirit Realm

i dont see how it would help kill a raid mob since when it triggers you cant cast anything so you might be able to live forever on a raid mob but doubt you could kill it

Preincarnation + AA boost + second chance tribute puts you over 100% proc chance of death save, buff blocking it blocked the DA portion, so every hit you took proced the death save where you didn't die and weren't DA, as long as the mob doesn't DoT you, you end up never dieing to the mob. There aren't many raid mobs with no DoT's for most part, but there are some and they can be taken out given enough time and the ability to beat their regen.