Do tell. Inquiring minds want to know.
Damage threshold allows bleedthrough even if you're attacking with a weapon that's too weak to penetrate. Enemies have the same benefit, leading to the whole Fallout 3 esque "shooting power-armored soldier to death with a BB gun" crap.
Fortunately, this is controlled by a single variable in the GECK, so sayeth Sawyer. My mod will change that variable to 0.
Later, I'll probably reintroduce DR to various armors in hopes of getting closer to that Fallout style, since DR is still a field in the GECK.