I view the numbers behind the game as the race track the cars are using. It provides the general path and definition of the area that the adventure is taking place in, but there are times where it makes sense to go outside the lines a little bit when it gains one an advantage.
So if a critical smite attack leaves a dragon alive with 1HP, then maybe it works a little better if that gets the kill instead of random NPC #3 punching it.
When this happens I always smile evilly and say "1 hp left! Bad luck!" and they groan. Of course if it had 27 hp left and they do exactly 27 hp damage, I tell them that too, and they smile.