Implications of the fixed damage model

I haven't seen any discussion over this other than the usual memes and/or whining but I did some maths and I'm not really sure what to make of it. Maybe BSG needs to make a change, maybe there isn't an issue at all.

Because all damage now evenly spreads to the remaining healthy limbs after a blacked limb gets hit, you only need to get to 210 damage done through a blacked leg in order to zero the head and result in a kill. This is because the head has the lowest HP and results in death if it hits zero via damage so 210/35 = 6 or the remaining healthy limbs left to take the damage.

This seemed fine until you actually consider the TTK potential here. Just a few examples:

G18c with RIP ammo: 1200 rpm, 102 damage per shot, 3 shots to kill. 50ms between shots means 100ms TTK if you land all 3 shots consecutively on one leg.

Vector with .45 hydrashock: 1100 RPM, 105 damage per shot, 3 shots to kill. 109ms TTK.

PPSH with PTgzh: 1000 RPM, 55 damage per shot, 5 shots to kill. 240ms TTK. (The only reason I bring this example up is because it's so cheap)

Doesn't this seem REALLY low considering some of the top tier options best case scenarios are:

SA58 with two m61 to the chest: 85ms

HK with three m995 to the chest: 141ms

Obviously this is disregarding headshots, distance, and cover but still. Why pay all that money for a meta setup and armor when you'd kill faster with a vector and flesh ammo and have an easier time doing it because you just cut their movement speed by 80%? Why even bother with any of that SMG stuff when every 12g shotgun now has, in theory, an INSTANT TTK because they can do over 275 damage in a single shot?

TL;DR: Time to kill at close range has become practically indistinguishable between very cheap weapons and the most expensive weapons in the game.