edit: They don't. It's just too long. I completed it on master in the end but missed one champion because I had enough. Very poorly balanced for solo play. :/
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Update: After the hell I went through on master difficulty I decided to farm for Loreley Splendor on Legend. Dropped in an engram on the 5th try in 6 minutes. Much better balanced. I wish the game had more opportunities to farm for specific items like this, namely mods.