It seems not all bosses can give all pieces of a set:
https://forums.elderscrollsonline.com/en/discussion/646311/endless-archive-set-curation-broken
Also the patch notes have a curious word here: “Curation rules in Endless Archive dictate that you will find your class’ set items first. After receiving the possible entirety of your class item set, you will get drops from the other classes.”
All class sets have all items available. So what purpose does the word “possible” serve unless there are circumstances in which it is not possible to drop some of those pieces from that encounter?
Also the patch notes have a curious word here: “Curation rules in Endless Archive dictate that you will find your class’ set items first. After receiving the possible entirety of your class item set, you will get drops from the other classes.”
All class sets have all items available. So what purpose does the word “possible” serve unless there are circumstances in which it is not possible to drop some of those pieces from that encounter?
It seems not all bosses can give all pieces of a set:
https://forums.elderscrollsonline.com/en/discussion/646311/endless-archive-set-curation-broken
Also the patch notes have a curious word here: “Curation rules in Endless Archive dictate that you will find your class’ set items first. After receiving the possible entirety of your class item set, you will get drops from the other classes.”
All class sets have all items available. So what purpose does the word “possible” serve unless there are circumstances in which it is not possible to drop some of those pieces from that encounter?
There could be a point where you have all weapons collected for all sets (or your class set) but still not all body pieces. So weapons will be random pulls from random sets while body pieces will still be curated to drop the ones you are missing.
For example, I have completed all the sorc weapons and am now getting random curated drops from other class sets whenever I reach a boss that drops weapons. Still have around 7 body pieces left to collect for sorc.
Also the patch notes have a curious word here: “Curation rules in Endless Archive dictate that you will find your class’ set items first. After receiving the possible entirety of your class item set, you will get drops from the other classes.”
All class sets have all items available. So what purpose does the word “possible” serve unless there are circumstances in which it is not possible to drop some of those pieces from that encounter?
The word possible here means exactly that, possible. You got all the items possible from that boss, which in this case is jewelry/weapons. The boss doesn't drop armour therefore pulling from that pool is not possible. It is most likely working as intended, just not how players expected.
Edit: Most likely the intended design was people run Act 1 more than succeed on Act 2/Marauders so you can fill up your book with armour before weapons, but this doesn't seem to be how it played out. Thankfully Act 3 onward doesn't just drop weapons.