The problem is armour, that's it.
Weapons should be lethal. If you're sat wearing a t-shirt and joggers (essentially peasant gear), and someone swings a sword at your chest, you're going to be fatally wounded most likely from one swing.
Now if I'm not mistaken, plate armour was effective at preventing slashing and cutting. It wasn't as effective at preventing piercing damage - and Chainmail was effective at preventing piercing damage, but could easily (in regards to what it actually is) be broken by excessive slashing and cutting.
So... there's the problem;
1. No Armour prevents mortal wounding to the point where a single slash, or single arrow, cannot actually kill a target (unless headshot).
2. Plate Armour doesn't prevent slashing damage much, its barely different than having no armour.
3. Chain Armour doesn't prevent piercing damage any more than plate armour would, which is essentially the same as having no armour on.
All in all;
Armour is broken.
Armor is broken and useless in game, yes. However, you got that one all wrong. Plate armor was effective against everything, mail was effective against cuts.