I noticed with 5 bloody beaks equipped, my bonus damage was equal to D * (1.6) * (1.03). There was an additional factor of 1.03.
The chest farming odds are way too low, not sure how you're doing it but id keep track of the number of chests per enemy, and have a function that lowers drop chance based on how many times they've been killed in some amount of time, with a minimum value based on the bonus drop chance. For example the drop chance could be the maximum between 10% of the bonus chest drop chance from rare aura, and the regular drop chance divided by the square of the product of the number of times an enemy has been killed within in the past 5 minutes and the number of chests its dropped in the last 5 minutes. This has a lot of upgradable parameters, for example lowering the kill count time window from 20->15->10->5 minutes, 0r increasing the percent of your bonus drop chance to have as the minimum value.
P = max( 0.1 * bonusChance, dropChance / pow( this.recentKills * this.recentDrops, 2) )