About RNG..

[Wobi]

The issue with coil is that for whatever reason they did not split the available loot evenly between the chests in Turn 1. All of the primals however are one chest, now there is a higher % chance of seeing a book drop but they are two different classes at 50 so that does not count. You would need to have someone gather the information from at least 1000 or more kills to determine if there is truly a skewed pattern for drops. Obviously this could be the collective information from several players.

Personally I've seen one bow drop in around 120 Garuda kills which would illustrate for me personally a .0083(Repeating of course) drop rate on the bow. I imagine another player has a much different drop rate out of their set.