And here is the argument I make against the argument that their power justifies rarity.
The ethereal is really just a legendary power affix with the special ethereal affixes and an added passive. Passives themselves don’t really increase your power level, and by the time you get to the 5th best passive for a build its pretty much utility.
That means the added power that’s being justified by rarity isn’t actually that rare. By the time you’ve gotten to GR90 you’ve likely gotten 1 or more ethereals already. What’s rare is the convenience of being able to play whatever build you wanted.
Ethereal drop rates that are too low don’t make the power creep rare, it just makes it inconvenient. I may have wanted to play Frozen Orb but I got a Twister ethereal instead. I could wait for a Frozen Orb ethereal to drop or I could farm Twister gear and make use of this powerful ethereal weapon that dropped.
This is different than other games where a whole class of powerful weapons would be on the same rare tier. Here, 1/100 isn’t that rare given how fast legendaries fall. But 1/100 plus 1/3 ethereals, plus ~2/15 legendary affixes…plus a passive…that’s what makes these things rare.