Since the devs increased the legendary drop rate, a few interesting things that I (and most of the people I run with) did not realize could happen have come to light.
Apparently, it is possible for a single boss to drop multiple legendaries for a single kill. In addition, it is possible for both of these drops to be the exact same legendary. It’s also patently obvious to pretty much everyone I run with that the loot tables are not balanced (e.g. you have a higher chance of getting X legendary than the rest of the loot table). Also, as far as I know, the double drops for each boss have also always shared a legendary with all other double drops from that boss (e.g. the double drops are either XX or XY but never YY).
Let me drop some numbers first. I have been farming Sentinel a lot trying to get a Stolen Edge of Arcvynorr. In over 100 completed runs (and a number of runs where the Old Sentinel glitched), I have gotten 7 Songs of Vigor (only 1 before the legendary increase), 1 Vigilant Power Scouter, and no Stolen Edges or Vigilance Links from the Old Sentinel; 2 Vyn’s Quivers (only 1 before the legendary increase) and 6 Chrono Keys from Vyn; and 8 Guardian Shieldbreakers (only 1 before the legendary increase) and 2 Symbiotic Gauntlet (both before legendary increase) from Arc.
Based on these numbers (admittedly a small sample size), before the legendary increase, the drop ratio I got for Sentinel was 1:0:0:0, 0:1 for Vyn, and 1:2 for Arc. While it’s not particularly robust, it’s reasonable to assume that there was either an equal (or at least close to equal) chance for each legendary to drop.
After the legendary increase, these ratios went to 6:1:0:0 for Old Sentinel, 6:1 for Vyn, and 7:0 for Arc. This suggests that something extreme was done, but only to one of the items in each loot table.
As such, my theory is this. On the back end, when a boss is killed, the game makes 2 checks in addition to all of the other normal loot stuff. One check is to determine if a legendary from the entire loot table drops while the other is simply to determine if the “common” legendary drops. It’s possible it’s been this way since release (if there have been cases of double drops before the legendary increase, that’s confirmation), but, based on my own (admittedly meager) data, it’s obvious to me that the devs didn’t globally increase the legendary drop rate: they simply increased the chance for the common legendary by about 5 times.
I’d be interested if anyone else has anything else to add to this (it would be really awesome for a developer to either confirm or deny this too!).