A big part of our problem is that when we talk about weapon damage, we talk about fatigue and wearing a combatant down until the one crucial strike that turns their birthdays off-- and whether we're talking blades or bullets, armed combat just doesn't work that way. If a knife fight or a gunfight somehow lasts longer than six seconds... well, there's the shots/strikes that end the fight and there's the shots/strikes that don't matter.
Brain, heart, lungs, spleen, liver, kidneys, spine... those will end the fight immediately, maybe lethally. Major arteries in the shoulder and inner thigh, you're dead within a minute, but you're still fighting that whole time. Bladder, bowel, intestine, those will kill you in three or four days with only a marginal decrease in your ability to sustain a firefight. (I would imagine the pain would be more of a hindrance to melee, but...)
But the defensive wounds you get all up and down your hands and forearms from a prolonged knife fight? They're not what's slowing you down. Long, shallow cuts along the outside of your forearms will never kill you, and they'll only have a serious effect on your ability to keep defending yourself if they catch the tendons in your wrists, or if you're not wearing gloves when the blood starts flowing. It's the effort of defending yourself that wears you down, and from personal experience-- years and years of personal experience-- there isn't that much difference between stiletto fighting and flamberge fighting because they're all wrestling anyway.
If you take one bullet in a vital region, you fall down and stop fighting and probably die. If you take one bullet in a non-vital region, you keep fighting and you go to the ER afterwards and... there really isn't a whole lot of in between as far as gunshot wounds go. If you take thirty bullets in non-vital areas, and nothing touches the birthday control centers, you walk to the trauma surgery yourself and you're home in time to get enough free drinks to offset your hospital bill.
D&D combat most resembles a boxing match, and the reason boxing matches last as long as they do is that the rules don't allow the means to end them faster. You can't land a knockout punch on a well-trained and well-prepared opponent until you've compromised their ability to resist you, until they can't get their hands up or their chin down fast enough to stop you.
Ironically, in the d20 Modern rules, they took the one thing that the D&D combat system actually represented well... and made it use a wholly different subsystem.
And shields, shields are dramatically and tragically underrated. As long as your enemies are in front of you, a good stout shield is better than head-to-toe maille and gives you the option of trading your arming sword up for nice hammer or axe.
