Well I grant powered armour and whatnot may make a difference, but you would be surprised how little weight does. If you had a two kilogram sword and did that while I swung a 700gram mace/hammer/etc at it I would easily smack it out of the way, jar your arm and possibly break it which wuld be the least of your problems because my macehead would continue on into you at speed. While the sword may weigh more and have more momentum, the weight of the hammer/mace/etc is focused at the tip meaning it has far more rotary power (I think that is what is called anyway, I forget)
Its not really a criticism of the game, its fantasy, who cares, I just get annoyed when I see fighting styles that make no sense. Like florentine (duel wield swords), looks flashy, completely impractical.