People Can Fly will release an Outriders patch next week, which will significantly increase the drop rates of legendary items. Some items can only fall from enemies of certain levels or higher.
In addition, legendary items will be prevented from having more than one. This event means that if you have a legendary item in your inventory or stash, a duplicate item will be discarded.
Boss loot in story mode will include all non-class Legendary Helmets. According to the developers, this change will increase the variety of items.
This patch is currently being tested and is expected to be released early next week.