After 100s of chest pulls at r3/r4 it appears that reaper loot no longer pulls at legendary (30 and above quests) for lower reapers. I play 90% of my gameplay at r3/4 solo or with a fixed group that report all loot to me. I have however had enough loot at r3/4 to take a one sentient jewel from sentient jewel 150k to 210K and another from from 60k to 100K (assuming three legendary items per 1000 sentient xp, that means I have pulled at least 280 items with no reaper on them) and assuming my buddies pulled half as many (group of 4) , lets assume another 150 items were pulled.
Even if i drop the pulls down by 100 from items pulled from raids (I do maybe 15 of these a week, mostly at LH)) that means more than more than 300 items without a single reaper item for mostly r3/4 dungeons.
It appears that reaper stuff still appears at heroic at r2-r4, but never at legendary content.
I do not start getting any reaper items until r5 or above on legendary. then the rate seems around 1-2% at most.
And NO, the solution is not to start doing higher reapers if this is not intended to be the case. Also, I used to get reaper items in the past at lower reaper levels so this is a more recent problem with loot tables. of course this could be an intended change, but it seems a bit unfair to the non r10 capable characters that are willing to accept lower drop rates, but not non-existant drop rates.
For Epic dungeons , i do not farm items, so usually doing at r1 or elite, sometimes hard. So have no real info at those ranges.