I know that a dozen or more TTK posts have been on this forum since the devs started it from for the open beta, but I felt that I could:
shed light on both the issue
decrease some of the toxicity that's arisen due to honest misunderstandings on both sides.
Low VS High in TTK, and why both sides feel the others are either outright wrong or 'casual':
I think there's a fundamental confusion at play here, none of the people I've seen wanting a higher TTK are asking for a 'casual' experience, they want a 'realistic' and hard-core one. IRL, body armor at level 3 or above will save you from several rifle caliber shots, with bruising only for the first few.
On the other hand, the TTK should be lowered people are pursuing what they consider to be realism but seem to believe that a rifle bullet can one hit a person in heavy armor (at least in the non-exposed areas) which is incredibly unrealistic in a modern scenario and would only make sense as a 'hardcore' experience if it was a WW2 or Vietnam Era game without any body armor whatsoever. Even one 9mm or .45 to the torso of an unarmored opponent isn't guaranteed to incapacitate, that's why IRL, police are trained to double tap armed suspects..
The game with the closest depiction of real body armor is Escape from Tarkov, which might be a little too much for my tastes, especially as we're playing as relatively poorly equipped forces. But if we had to shift the game, that's the direction it needs to shift from source insurgency.
I think the biggest reasons for a perceived too high TTK is the lack of reaction to getting shot, ideally a hit should cause massive aimpunch and sway to simulate the nasty bruise a stopped rifle shot will still produce. That will stop people from calmly turning around and headshotting you in turn, and make positioning and tactics all the more important!
For balance reasons, I can see why heavy armor could always be made a point more expensive, and slow users more, that isn't an issue of realism or hardcoreness at all, seeing as there all kinds of IRL body armors.
Also, now there's a use for proper sniper rifles for sniping as opposed to scoped ARs, as they're much more likely to guarantee a one hit kill at range.
There's a good reason that if given the choice, most soldiers in real life prefer body armor for engagements, as well as why militaries that can afford to gladly buy it for their men. The increase in survivability and increased combat effectiveness from the knowledge that you're unlikely to be one shot by an unlucky round is absolutely worth the money.
On a slight tangent, I think 5.56 and 7.62 could be meaningfully differentiated on the basis that 5.56 has better armor penetration than 7. 62x51, so 5.56 could say take one fewer shot to kill, but 7.62 would slow and inhibit the armored target more. Also, the higher caliber rounds should be better at penetration buildings, so wall banging becomes a more viable playstyle. They might cause greater suppression effects too for near misses.
On an even greater tangent, the game sorely needs not speed, but momentum. Right now, just bumping up the TTK makes running in zigzags like a DayZ mod era character a viable rush strategy. Not only should getting hit severely slow you down, but being able to spin like a dervish and instant acceleration need to be removed. For people who feel that this would decrease the skill ceiling and prevent quick aim in slower, indoor encounters, I would point out the game already features guns that go misaligned with the centre of the screen on small motions, this could be more prominent for heavily armored characters, depicting the soldier preferring to angle his gun in the direction of the target rather than trying to complete turn around. Knowledge of how that works would be a great compensating factor without letting someone 180 while scoped and under heavy fire.
I think I've addressed the realism and hardcoreness aspects of the debate, but it's always possible to disagree just on personal taste. I only request that if that's the case then it be said aloud!
Let me know what you guys think