I've always allowed a certain amount of ambiguity in combat, especially with regard to the apparent "logic" of "always" performing coup de gras actions during or at the end of them. The reason being, is that, while it may seem an obvious action to take, it's, for the most part, it's not as obvious at that. Combat's are messy affairs, and death is not always instantaneous nor the cause obvious. Blood splatter, Bruising and wounds can make someone "appear" dead, but they are actually just unconscious, or very, very, good acting that way, and also, quite often the combatants simply are distracted or have little time to fully understand the nature of the wounds their previous opponents have suffered. Besides I'm as happy with the occasional "miraculous" survival against the odds for an apparently mortally wounded NPC as I am for a character. This is especially the case in larges battle with many combatants involved.... where there are so many wounded and dying that it's often a very confused affair. My thoughts often go back to watching a rather comedic scene in a chinese film "Zu Warriors" where 4-6 armies simultaneously battle each other, then just after the heroes depart, everybody gets up, as they were all acting dead.
