Usually any time my group impliments some kind of numerical damage reduction we also use a minimum damage rule. basically just have the ability to tank up be there, but attacks will always do at least one damage.
4 years ago (+2)(-1)
So what I've decided is that the shield and Helm roll their usage die immediately and prevent damage and take a usage only on a 4+. So if you are wearing all three and you take 5 points of damage you roll a die for your shield and a die for your helm. Lets say you get a 5 for the shield and a 2 for the helm. Your shield takes one point of usage and you take 3 damaged (5 - 1 armour - 1 shield). The armor only takes usage damage at the end of combat, and as before you can sacrifice your shield at any time after finding out the result of an attack to cancel it entirely.