I'm arguing with a weird inversion that Ahnehnois and Saelorn are pushing where, after you've settled on your abstractions, you turn around and declare that those abstractions must also be directly observable physics of the universe. This goes to Fighter Bob knowing exactly how many arrows Ranger Jeff can shoot at him before he keels over. (As opposed to this information being known only by their players, Beth and Jenny.)
The really important part is that the average number of arrows to drop someone is an objective part of the game world (for whatever definition of "hit" you want to use). Whether that's a scratch, or a direct impact against armor, or extremely-close shave - or even if it's left undefined - as long as the reality of the arrow is mechanically reflected as d8 damage, and the state of the character is mechanically reflected as a number of hit points, then it will be true that it takes about the same number of arrows to go from full to zero (barring outside variables, like critical hits and sneak attack and all that).
You may choose to not describe those in a way that's directly observable, but it's still "observable" through its interactions with other sources of hit point damage. The effects of an arrow that "hit" when nobody was looking can be still be observed indirectly, when the victim drops from damage that would have been barely insufficient to drop the victim if she hadn't been previously "hit" by the arrow.
Personally, I choose to describe things in the most direct way possible. When I play, a successful attack is always visible as such to anyone watching, and almost always elicits a grunt or a yelp of pain. I also play hit points as observable to anyone who looks (at least as a rough estimate - down to half, about ten percent, barely standing, etc). This isn't strictly necessary by any means, but one of the primary jobs of the DM is to let the players know what their characters observe within the game world, and keeping such a simple translation for every game mechanic makes it much easier to keep everyone on the same page; it's much less work all around to just say that someone is hit and subsequently damaged (optionally describing the hit and damage in greater detail), rather than sorting through the myriad of alternate explanations and then explaining that
this time the thing that I described as a narrow miss comes out of hit points instead of AC.
It also has the nice side-effect of keeping all player information within the realm of PC information. When the characters can
see how injured they are, it allows them to make the same decisions as the players when it comes to casting Cure spells or drinking potions or whatever. When I describe a direct hit that fails to make a dent or draw a response from the enemy, the PCs and players can both learn that the enemy is somehow immune to the damage dealt. It cuts down on confusion.