Finally got around to compiling this… sorry for not sharing earlier. Not counting ethereals from Djank, here are what my ethereal drops looked like. I played 6 classes, no necro and got to paragon 1600 on the PTR.
Ethereal drops of normal ethereals, non-ancient:
I leveled 2 different toons from 1-70 Solo, self found. The DH did Nephalem rifts and found 14 ethereals before lvl 70. The monk did a mix of bounties and massacre chaining and found 9. Did not think to do vaults on either, unfortunately.
I did not keep track of individual class play time, but reached about the same paragon as I would if I played a whole season kinda casually and found just over 400 ethereals. 117 of these in 23 ancient vaults. I found 2 necro ethereals, both in ancient vaults, even though I did not play a necro.
I don’t know what the increased drop rate is for each of these activities, but have heard its like 20x in PTR outside of greater rifts? Of course, xp is also hugely boosted. Hope this data helps somewhat.