Also, outside of this rather small detail about resistance shred there isn’t any other mention (that I could find) in the Game Guide. Trasochi’s explanation of shred (or something similar) would likely make a great addition to the Game Guide;
Some additional points to include in the description of shred;
Armour shred stacks do not have a cap (unlike resistance shred) and can shred armour into the negatives
Resistance or Armour shred effectiveness increases the effect of each stack of shred. And then include a short example for one or both, such as; Normally 1 stack of armour shred reduces armour by 100. Having 50% increased armour shred effectiveness would increase each stack of armour shred to 150.
Each stack of shred, be it armour or resistance shred, lasts 4 seconds