Armor does matter. For example, you 1-2 hit most people, no matter if they use armor for 2k or 8k, right?
But look at low level chars (aka peasants) - if you use 2k armor, you have almost no protection vs them. Few hits and you die to peasants! Shame on you! But if you use 8k armor, you won't die to a peasant in 4hits, but in 7hits. That IS the difference.
Same vs archers.
+ there is just too many of str chars, that's why armor doesnt matter too much vs high level chars - if someone has 10 ps, he is going to 1-2hit you no matter if you use lamellar vest or banded armor