That would create a lot of problems though. People could play PCH+Wrath after an opponent played Aocp or something. Essentially any battle winner off an interrupt play next would circumnavigate a CBN battle winner. I think of it like this if something cannot be negated it essentially nullifies all other negates (no negate can actually serve its purpose against hp) that you would have normally played otherwise, thus, in this scenario, blessing is not a negate. So then, if you can only play negates when you are losing the battle, and blessings is not a negate, you cannot play blessings when you are losing the battle. That help?