In Battle MP 1409, we just had this happen: I attacked phaselock's Human Warrior, so I know I was facing him. My character (Human Priest) had 9 health left and Guardian Angel in-hand, plus the revealed default Run. phaselock then did this: Code: BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Msg=The active player is now phaselock stopTimer 1 831 BATTLE LOG: Player=phaselock,Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Event=PlayAction,Action=Devastating Blow,Instigator=HW_test1,Targets=Divina startTimer 0 878 BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Msg=Divina took 9 damage BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Msg=Divina died BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Group=Divina,Event=Discard,Card=Demonic Miasma BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Group=Divina,Event=Discard,Card=Run BATTLE LOG: Scenario=MP Dungeon,Room=Battle MP 1409,RoomID=7299,Group=Divina,Event=Discard,Card=Guardian Angel Behold the lethal Devastating Blow, delivered from the front, which ignored Guardian Angel. The computer likely couldn't tell that the damage boost (Devastating Blow does 7 +2 per each revealed card) would bring it up to my Priest's 9.
Same thing goes for buffs and triggers but i do agree that in this case its a bit of a different matter.
Mentioned in the past with raging strike and other similar effects, seems to happen rather often with Guardian Angel not proccing when there's extra damage.