Howdy all! With Update 82, we're changing how Monster DR functions. Rather than each monster having its own DR value, failing to break DR will now reduce your weapon damage by 50%. This means that if you're fighting a monster that used to have DR 10/good, and you don't have a Good aligned weapon, rather than subtracting 10 damage from your weapon attack, your attack will now do 50% less damage.
Player DR is unchanged and will function how it does currently.
Note: This change has horribly broken the raid The Hound of Xoriat as Xyzzy uses DR to prevent player-sourced damage - this will be fixed for an upcoming preview!