So it sounds like for most people so far (unsurprisingly
), HP is damage absorption regardless of whether any effort is being made to withstand attacks. So it would be perfectly reasonable for an NPC to not make any effort in a combat situation and they would get all their HP? They could just stand there and absorb the generally lethal blows and be fine?
Do you see why I feel differently?
I can understand why you feel differently. However, I think you might be allowing "realism" to override several points (most already made, but I'll reiterate):
For one thing - this orc is on guard. It isn't that he's actually helpless - tied up or unconscious. He is bored, but not insensate. He can still hear the twang of the bow in the distance, is still able to move, roll with the impact when it hits, and so forth.
For another thing - this is an Olde Tyme LongeBowe. Not a sniper rifle. It uses subsonic ammunition, large enough that wind effects are very significant. Yes, skilled archers are awesome, but they aren't modern sharpshooters. Perfect shots at long range targets that aren't perfectly still (this guy isn't an archery butt - he's a bored orc who will be shifting around) are hard.
Yet another thing - the game already has rules for
exactly this scenario (the target is surprised, and does not see the attacker). That design is purposeful (see below). You can, of course, change that, but then the new ruling will take precedence. The players will expect every time that they can bypass hit points if they can attack unseen and from surprise, and if you try to enforce the old rules instead, you'll have to argue it every time.
Yet another another thing: You'll have to ask yourself why the bad guys aren't using the same tactics at every possible turn... Surely, it isn't like the PCs are the first to ever think of getting the drop on someone! If this is possible, what creature with a brain in its head is going to fight in the traditional manner, when they can just bypass hit points entirely? This structure is to keep the fairly cinematic normal combat form viable. If you introduce "but folks can be killed outright on a stealth attack" that will substantially change how the world works. For one thing, the adage in a world where this happens is "a bored guard is a dead guard" and the likelihood of the orc being found in this situation would be low - he'd not be in the open, he'd be hidden or under cover that would allow him to see without being targeted. He'd have a partner that would help him stay alert, and so on.
Yet another another another thing: If you, the GM, wanted the possibility that the orc would be killed in one shot, why didn't you make him a goblin, or some other critter that would be killed in one shot? Rather than change the rules, why not just have low-HP guards?