Elsewhere i read about drop of items being related to mission level and that for certain legendary drops you needed missions be like 7 levels higher than your own level.
I can´t find that info again, thought it was on the compendium but it isn´t. Im afraid the compendium is not accurate anymore on certain aspects and that there is important info missing, with patches and stuff changing the mechanics and the info written there.
I should please ask to update the compendium with the latest changes as some info may be missing or be innacurate.
EDIT: Found a example of info on a post around that may be missing from compendium:
[...] There are a couple rules for how and when item level 90+ drop can happen. First, 90+ items will only start dropping in missions at least 7 levels higher than your current level, and they cannot roll higher than your current character level. Second, the actual level of item drops are randomized, so you have a relatively small chance of seeing a 90+ item and you'll still see many level 90 drops. The chance to see a 90+ drop increases roughly linearly with each additional mission level beyond 7.
Example: To have a chance to get a lvl 97 item you have to be at least lvl 97 and you have to run a lvl 104 mission at the very least. (See, I told you that the new tarot mission scaling changes would come in handy.)