On skipping to-hit, or lethality vs transparency

JOESKY TAX - THREE MAGICAL DAGGERS (for Into the Odd, d6 damage)
Anti-Knife - looks like a dagger handle with no blade, getting stabbed with it feels relaxing and soothing and won't startle an unaware of sleeping target - the wounds only show once the blade is sheathed.

The Rusty Screwdriver - stains your hands with rust when handled. When you inflict a scar or critical damage, the blade breaks inside the target and starts rusting their body as if it were metal. The next time you go to sleep, a new blade grows out of the stain on one of your hands, dealing damage directly to STR.

Singing Couteau of Mr. Wallie Wells, Esq. - an incredibly fancy kitchen knife covered with fine engravings and a cristalline blade. Worth 1.000£ to the right buyer, breaks on a damage roll of 6.

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Here is the process, both in-fiction and mechanically, for what happens when people hurt each others in a few games. I'm skipping initiative and potential modifiers and so on, as I really want to talk specifically about the idea of "to hit" and "damage" vs HP, and the harmony or dissonance between mechanics and diegesis.

Dungeons & Dragons (and most traditional tRPGs)
1. Character attacks Target, Roll to Hit.
2. Attack Hits! You must now roll for Damage.
3. If Damage is equal or higher than Target HP, they're dead or out of action. Easy.
4. If Damage is equal or higher to some threshold value (50%, 75%), describing wounds is considered.
5. If Damage is not enough for either 3 or 4, either the target was hit but superficially so, or parried, or dodged, etc. It's all appropriate descriptions for this result. Maybe you add that they're getting tired.

2. Attack Misses! Either the target was literally missed (somewhat unlikely) or it was hit but superficially so, or parried, or dodged, etc. It's all appropriate descriptions for this result. Maybe you add that they're getting tired.

Classic Traveller (1977 or 81 prints)
1. Character attacks Target, Roll to Hit.
2. Attack Hits! You must now roll for Damage.
3. If Damage is enough to lower one stat to 0, the target is stunned and out of action.
4. If Damage is enough to lower two stats to 0, the target is wounded and out of action.
5. If Damage is enough to lower three stats to 0, the target is killed.
6. If Damage isn't enough to lower at least one stat to 0, either the target was hit but superficially so, or parried, or dodged, etc. Appropriate, tired.

2. Attack Misses! Either the target was literally missed (somewhat likely with firearms) or it was hit but superficially [...] you get the idea. Starting to see a pattern here?

In both games, we can see that there is little difference or reason to differentiate between a miss and a low damage hit. In the fiction, there is no reason why a miss wouldn't be as taxing for one's stamina than a superficial hit if we consider HP/damage to be abstract enough that not every loss of HP involves actual wounds (which is another conversation, but one that I think most people already agree on at this point).

(Note: I love both of these games. I just need to point out this aspect of what has almost always been common wisdom (mechanizing "to hit" and "damage" separately) in tRPG design, to put it in contrast with other approaches and why I enjoy them more.)

Maze Rats
1. Character attacks Target, Roll to Hit.
2. Attack Hits and the damage is the difference between the roll and the target's AC-equivalent.
3. If Damage is enough to bring the target to 0 Health, they're dead. Otherwise, they're probably wounded because you don't get a lot of Health (HP) in Maze Rats. You get 4hp at 1st level, and only gain 2 per level.

2. Attack Misses and you can describe it as an actual miss or a superficial hit.

I like this better because the low HP means that you'll almost always have a clear difference in describing misses and hits. It is somewhat common to miss, though, if you get an unlucky streak. That means some combats might drag down a bit longer than they could, but with good descriptions and tactics it should increase tension, and provides a solid "classic" take on simulating violence without the problems I described above.

Troika!
1. Both fighters Roll to Hit.
2. Highest roll damages the loser. Here there's a fair chance that the few first rounds won't result in very dangerous wounds, but someone is losing Stamina (HP) every round, so at least things are moving forward. It can take a while though if you're unlucky with damage.

I suspect Daniel Sell just doesn't like tRPG violence and so made that sub-system somewhat bland so that people don't resort to it first hand, which is commendable. Initiative is super fun though. Anyways my point is: here is another approach where you get at least some degree of harmonious mechanical and diegetic consequences for every attack.

Now let's get into the really good stuff because I'm trying to make a point and you don't have all day.

Into the Odd (Electric Bastionland)
1. Character attacks Target, roll for Damage
2. If Target has Armour, reduce damage by 1 or 2 (3 if it's a dragon or something).
3. If Damage isn't enough to bring Target to 0 HP, it's the same as with OD&D/Traveller and also works for describing "misses". If no damage is taken due to armour, it's a good opportunity to use armour in the description.
4. If Damage is enough to bring Target to 0 HP, a bunch of interesting things happen: at exactly 0 HP you take a Scar, and below you take STR damage, which represents actual wounds, and you need to roll for Critical Damage.
5. If Critical Damage is inflicted, the Target is out of action.
6. If not, the Target is wounded but still able to fight back.

Now, this is great because it gives the same range of possible results as AD&D with the optional but often used "death at -10" rule, without any of the tedious bits. You can attack someone and make them closer to being down (HP loss), you can wound them (STR loss), you can take them out (Critical Damage) and sometimes you can kill them outright (STR=0). It's also pretty fast. Maybe a second or two less fast than when the only health pool is HP but that's balanced out by the kinetic fun of rolling a bunch of different polyhedrals.

I've run a lot of Into the Odd and what I've noticed is that in practice, it is less lethal than OD&D. I think the reason why is transparency. See, in OD&D if you have 8 HP, you might take 2 Hits, or you might take as many as 8 Hits depending on RNG. Especially for begginers or people who don't care/think much about the rules when they play (they're playing the world, see, not the system), ItO is much better at telegraphing danger: NOW you're out of buffer and the next hit MIGHT put you down but you still get a chance to run away or parlay or find a better tactic than "I swing my axe at the ravenous taxman". And even if you don't, you're probably dying but not outright dead. This is cool because instant kills become shocking (cause rarer) moments, but you still don't want to fight "just for the hell of it". In essence, even though it might look more punishing, it's actually much nicer than OD&D in practice. In that campaign, we had about 14 deaths using OD&D over two sessions, and 2 using ItO rules for eight sessions, with the exact same players at the table.

Any Planet Is Earth
1. Character attacks Target, inflict Damage (it's often a trade-off since there initiative is simultaneous)
2. If Target has Armour, reduce damage by 1 or 2 (potentially nullifying dumb brute force, though you can still bypass armour with clever tactics, positioning, etc.)
3. If Damage is enough to bring you to 0 Hits, you're dead. Otherwise, you're probably wounded since you don't get these many Hits, it's all dependent on the situation and weapon used.

(House Rule)
4. Being brought to exactly 0 Hits makes you dying instead of dead, whereas getting into the negative makes you dead-dead, to allow for the occasional "should we grab our buddy and get out" dilemma without making it a safe, near-automatic buffer.

Now we're getting into crazy lethal territory right? Not only is damage the direct result of attack (no to-hit) but it's a set number that is dangerously close to PCs Hits. A sword is 2 Hits, a gun is 3 Hits, a rifle is 3 Hits and a PC has 4 Hits. A meat-grinder! Yet it's not.

In fact I've been running a few games using these combat mechanics with players of various experience and skill-levels and nobody has died yet using these rules. Things have been tense, and kinetic, and cinematic and exciting but no sudden death. That's because fixed damage increases the transparency even moreso than ItO did. When you run OD&D it's easy to disconnect the mechanics and fiction because of the many potentially samey outcomes I described above. It's still fun and exciting mind you cause you might die and all, but strategy and tactics aren't an absolute requirement for survival, so some players might miss out on that aspect and just brute-force their way through combat.

APIE though, because I'm telling you straight up "If you stand there you'll get shot for 2 Hits, you've got 3 Hits left, that ok with you?" and you have to tell me what your actual plan to survive and win the fight is on a moment to moment basis, is even more transparent. Sometimes you'll trade harm "you take pot shots at each others behind various cover, broken glass and scared birds fill the room and soon all you see is smoke", sometimes you'll use clever tactics and hurt them without getting hurt, or end the fight entirely. Sometimes you'll make gambits that are ballsy but might just work and it's going to be either or both of the latter two options most of the time because trading harm is not viable, long-term. This means death will not just rarely come without warning - it will never come without warning, and that is a built-in feature of the game. That's internalized player agency.

Making such a system less gritty is simply a matter of increasing Hits for PCs (my current approach, 6 Hits for PCs in Sword & Sorcery games, 8 Hits for a theoretical Myth-level game), and/or adjusting the Hits inflicted by different weapons, perhaps even ditching variable Hits per weapon for settings and tones where weapon differentiation is purely aesthetical (ie: you could have all attacks deal 1 Hit by default).

TL;DR
• Traditional to-hit + damage roll tends to create dissonance between dice rolling and fictional outcome.
• Direct damage intuitively looks more lethal, but is actually less punitive and more transparent than traditional to-hit + damage roll.
• Increased transparency leads to better player agency, which leads to more exciting play.