I don't if this is even possible but I did 60 raids in tier 20 and I got one legendary even though I had a bitgor. I know my luck is horrible but this seems a bit too weird to be happening or maybe the drop rates are scuffed.
#teir 20 raid
near spoke
opal cobalt
I got a 
on my regen runs this morning on a Super Scroll.
It's all 
umbral yoke
My rng can't be that bad
And yet it is.