My priest's Lifesaving Block didn't trigger when opponent's warrior hit her with a Devastating Blow. I'm certain I was facing the warrior and I have no clue what could have caused this. Happened today, I took the screenshot and copied everything from the console, too. The priest was standing on the red x. Hope it helps something. In LOG.png is the logged info from the last move and in Text.txt is the whole log. It looks better when copied into MS Word
Lifesaving Block only triggers if the base damage of the card is high enough to kill the character. Boosts do not count. The base damage of Devastating Blow is only 7 and your guy had 14 HP left. It's unintuitive but that's how that block card works.