[RyanW]

I don't think it should change much between 0 and 3. You're dealing almost entirely with muscle powered weapons dealing the same range of damage. If doing this, I might go with something like 5 points, minus 1/2 point per TL above 3.

On the other hand, I think low DR values retain a lot of usefulness. Most injuries that people face (even on the battlefield) are cuts, scrapes, and falls.