I'm not saying that armor is a weak skill; I take it as a priority after logistics, earth magic, tactics, offense, and archery, plus the advantage is that it always works, and the disadvantage is that it almost doesn't work if it's not a specific situation. I also never (and I can't) focus on dealing and controlling damage; instead, I focus on breaking through with minimal losses, killing everyone on the first contact, and not leaving (almost) anyone for a counterattack – that's what I understand.
Perhaps the trick is that to really increase damage, you need to level up (and find) a total of 2 skills, while to reduce damage, you only need 1...