With the release of Codex Adepta Sororitas and the upcoming release of Codex Inquisition, I see a potential for abuse. If you thought the screamer star was bad, this could take the cake!
This released image of the new Codex Inquisition would suggest they will have an option to take priests. If these are the same as the priests in the codex Adeptus Sororitas, then their is potential for abuse.
Now take this with some salt, as they would have to get the same rules. If they do not get the same battle hymns or if they are not Independent Characters, they will not be broken. Now let us suppose they are the same. I think their is a very good chance they will be.
I expect codex Inquisition to be battle brothers with all marine codexes. Take your Blood Angels codex. Use a unit of 10 thunder hammer storm shield terminators. Add Corbulo for feel no pain. Add a priest for fearless and hate. Battle hymns I would use the reroll armor and invulnerable saves one.
What do you have? You have a fearless unit, that rerolls the first round of combat, They can reroll their saves and get 5+ feel no pain in hand to hand. That's better than the screamer star. they also have a 3+/2+fnp Independent character that can tank the shooting wounds for them! And not to forget they could reroll one dice per game due to Corbulo's special ability!
So a lot of what ifs here, and several things can make it not happen. On Saturday the 16th of November we will see if it will be fully operational, or just destroyed by a lucky shot!