Does the Nameless Seer spawn less in more valuable maps?

As the title says , Does the Nameless Seer spawn less in more valuable maps?

I've noticed I've farmed around 140 Defiled Cathedral and no Nameless Seer spawn, but as soon as I jump to Jungle Valley 2 spawned in the first 10 maps?

Do we maybe have information regarding the spawn rate or something similar

P.S On the Defiled Cathedral I've noticed more spawn of Reflecting Mirror, maybe the ratios are bad??

P.S.S Does he still spawn after you kill the map boss(too many questions...