Yep, arena mode fighting proves hammer-wielders are much more effective than sword-wielders during a plate armored melee. Hammers are glancing off of breastplates, however, broken limbs, hands and skulls are more than enough to cripple the sword user before bludgeoning death rather slowly grinds them down. Swords have much more dramatic effects, however; I got quite lucky on my third fight and managed to take off the opponent's right lower arm. My sword-blows merely glanced off the victim, however, and eventually he bled to death. I've not tried fighting with leather or leather with hammer versus plate with hammer, but I have my guess as to how that would go.
Yep! My tests show the same thing, as well as that leather armour in all cases protects less than plate, and hammer/mace-wielders are more effective than spear-wielders against plate-clad enemies.
However, my arena tests with plate armoured individuals squared off against each other show that pikes are more effective than maces and hammers which led me to a possibly relevant observation and associated suggestions: I have reason to believe that breast plates and gauntlets do not defend the upper arms and shoulders, as these are what are predominantly damaged in fights between hammer/macemen vs pikemen clad in plate armour. Also, I never see strikes to the arms, shoulders, and neck damaging through the plate. If there isn't any plate arm, neck, and shoulder defense, then there should be!
Also, with regard to neck strikes, I never see neck strikes damaging through any of the other armour types, either. There should be appropriate neck defenses for those types as well.
Another suggestion while I'm at it: Greaves should be able to be worn in conjunction with chain leggings. I could nitpick about terminology used for the various pieces of armour as well... but that doesn't bother me too much.
Also, does weight of armour influence fatigue? I think it does, but I'm not sure.
Oh, and do fighters in this game realize when an opponent is sufficiently incapacitated to move on to another threat? I haven't tested this out yet.
And one final question... do long weapons like spears and pikes have a reach advantage? If they don't, they really should, along with associated disadvantages at close range if appropriate.