well this thread took a turn. if anyone is still interested: we've decided to just roll with combat luck stacking on armor for now. agreed as a group to re-evaluate if anyone thinks it has become a problem... tankiest character in the group is 9rpd/12pd with armor. it seems a little high, but were playing a more role-play heavy game, and hes still in danger of getting knocked unconscious. which to a degree makes sense to me..
if you gave me a normal person, even with a little above average strength, a long sword and told me to damage a competent maneuverable person in llamelar armor (he is suffering no encumbrance with his current str/weight) i dont think i could realistically do any body to him. now a person with training (modeled by str only with sword) that is capable of upping the damage to 2 and a half d6, is fully capable of knowing the right spots to hit to actually hurt the armored person.
as for the philosophical combat luck debate: Ive always seen it as a "grazed you" option. Arrow bounces off the armor, of if unarmored, scrapes the bone etc.... Sometimes we have fun with it and rename the power "Just a scratch!" or "Rolling with the punch." DND has similar mechanics in that if the monster rolls a 17 against the 18 AC fighter its more fun to say "His jaw snaps shut on your forearm but is unable to pierce the armor" rather than a simple "he missed"
i mean we could theoretically argue that hit points from DND and stun/body in hero are really just plot armor points, once you reach 0 you've expended your allotment of bullshit before the inevitable happens.