I got around 12 Pransker Sigils during the season. Each time I had of couple of them I would open the Party finder, find a group with low Paragon players doing NMDs and join them to share my Sigils. There are always low Paragon players.
Levelling the Essence of Sin to 5 was an extremely dumb activity. It took a few hours to achieve it but after that Tributes of Ascendance would start dropping like candy from the chests at Azmodan (…OK exagerating a bit). Got more Mythics from running the UC than from my Pransker Sigils.
I’ve seen plenty of offers in the Trade chat to join for free Mythic Undercity runs. Players had so many. Many opportunities for those you didn’t want to waste their time levelling their Essences but still wanted Mythics.
If next season we still get as many NMD Sigils as in this season, Pransker Sigils will again be available to many. But, just like in S11, it will probably take some effort to find one.
Can’t say for S12 but in S11 getting 5 Mythics from Bosses was harder than finding a Pransker NMD Sigil. At least, that’s my experience. I am not even sure I had 5 Mythic drops from Bosses during the season. Probably explains why I said Pranskers are a bit too much.