Are you sure that dmg done gives you more chance? I doubt that. Drop rates are fixed and posted on event topic 30% for void tile, 10% for paint and 5% for book. Dmg is just used as looting rights thing. Once you pass that, your every char has same chance of getting rewards as anyone else, only difference is that you have more chances. Just like a dice roll, you need 5 on dice to get reward, you roll your 1 dice i roll my 3 dices