Theres a huge difference in damage / defense when your item's durability got low. I remember sometime in phase 3, my bow actually reached 0 durability. I was trying to figure out why I was doing such ****** damage, I thought maybe it was because I was fighting level 20 mobs with a level 1 bow. But then I saw the durability >.>
I think I was hitting mobs for 20 damage with 0 durability. Around 100 at max.