A few details:
I only play advanced hardcore solo to grind legendary gear.
Here are my facts:
Fact #1) I have done ~40 advanced hardcore algorithm runs (confirmed through my stats page) and have in that time received ~20 legendaries (3 of those from ISIC, the final boss - I’m still trying to get the pacifier). Some observations from these runs: on advanced hardcore (not sure if it is the same on lower difficulties) I will often see a boss drop several items (but not guaranteed). Pretty much every time I’ve gotten a legendary I have seen at least two items drop. My guess is that the “extra” item is how advanced hardcore gains it’s higher drop rate that it purportedly has.
Fact #2) I have done the Renegade on advanced hardcore solo about 25 times. In this time I have seen 0 legendaries from Hylis (the only boss on the mission) and I have NEVER seen him drop an additional item.
Although I realize that it is possible that I have simply been really unlucky, my total drop rate on algortithm per boss is ~10% (20 legendaries / 160 boss kills is 12.5%. Let’s say I’ve done more boss kills since I used to sometimes die before reaching isic, and also that I’ve been lucky). Unless I’ve been incredibly lucky, this should be a ballpark good estimate on what the drop rate should be for an advanced hardcore boss kill. At this probability, the odds of me getting 25 non-legendary drops in a row from Hylis is 0.9^25 ~ 7.1%. This is still a fairly high probability, but this PLUS the fact that I’ve never seen hylis drop > 1 item (of any quality) seems a bit sketchy to me.
Even if this is not a bug, but intended behaviour, it is a bit ridiculous. 25 advanced hardcore solo runs to not see a single legendary from a boss is … obscene.