Realism is not a great way to balance a multiplayer game.
There is no "effective way" to deal with lordly armor.
Hit the head, most people don't have their helmet loomed (and even if they do, it doesn't change much).
Otherwise, you've got bec, morningstar, great maul or steel pick, which are probably the best tincan openers of their category.
I agree heirlooms nerf cut more than pierce, but it's the way it is. Cut weapons already have a lot of advantages over pierce / blunt weapons, they can't be the best at everything.