I have read through several conversations on this forum that are all about the same thing: The damage model. There appear to be two major groups, those who want a large number of hits to kill. And those who want just a few. The motives of the former group usually tend to appear to be concerns regarding weapon validity, difficulty of the game, variety etc. The latter group seems primarily concerned with realism, and weapon validity (from a different angle), the "intensity" that comes with sudden deaths that require few hits.
I am here to tell you all that both of these camps are wrong when it comes to how they would like to see the devs achieve their goals. There is a third option that everyone is ignoring because everyone here is debating this subject within the confines of the existing model, which to be honest is problem that just about every game has.
I also want to be clear that while this will concern "realism," this is issue has never really been solved satisfactorily IMO even by games that claim to be "realistic" such as squad or Arma. To lets leave the milsim vs esport party hats at the door, please.
I am going to start by explaining why both sides are wrong, and then give my solution.
Example 1, the high TTK solution. Its advantages and disadvantages. Generally I see people ask for something like this: 1-2 shots for full size 7.62, 3-5 for intermediate rounds, and more for pistols. With various variations for how armor plays in. The advantage of this scheme is that it increases weapon stat diversity and increases TTK. Stat diversity prevents reducing weapon utility down to just 1 or two stats, such as accuracy or ROF. Higher TTK means fights are not sudden deaths, and gives a unsuspecting player time to counter a bad tactical situation with higher DPS etc. The problem with this approach is that it is extremely unrealistic and results in usually making high damage per-shot weapons the best in the game. Basically, battle rifles like the FAL become king. If that does not specifically happen, then some high DPS weapon will be the weapon on choice. Ultimately, barring totally absurd variation in weapon recoil and other stats, you get a damage corridor where valid gameplay exists. Everything else sucks. In "realistic" games like ARMA where a system like this is used, you end up having battle rifles unrealistically take the top slot. In unrealistic games with this sort of system, you usually get very gamey adjustments to various other weapons to make them behave in ways that offset the damage issue. Without dramatic changes to INS, the former is likely.
The other major camp wants very high damage on all guns. This results in higher realism in certain dimensions, in the sense that in real life bullets are highly....lethal. Especially rifle cartridges, regardless of type. In reality, all the rifle rounds featured in this game are very strong and quite capable of 1 shot stops. They are also all capable of multi shot stops. However, the problem with this approach is that it makes all the guns "the same" in the damage dept and risks reducing weapon validity by some other metric, such as ROF or accuracy.
So in short, we can either have a large set of damage tiers, or a bunch of 1 shot or two shot stops. Both have problems both from game play and for realism.
What we actually need............is a variable damage system.
Something like this (this would be for center torso hits):
7.62x51---------------50% 1 shot stops. 25% 2 shots. 25% 3 shots.
5.56x45--------------40% 1 shots stops. 35% 3 shots 25% 4 shots
9mm--------------------etc etc etc.
I think you get the picture. Essentially, all center-mass hits should have a decent change of a 1 shot kill without armor, but smaller calibers should fail to do this more often and with lower possible potential. In other words, the max number of center mass hits 7.62 can potentially require will be lower of the number of potential hits needed by 9mm.
What this accomplishes is to be both realistic and solve weapon diversity problems. By extension, it allows for both high and low TTK.