I have a question

Advance chest are no longer found in end map wheel?

I think they are just more rarer those days.

Because the essence took up space

I guess it's still luck.
I got a cunning and a mind bending yesterday in those advanced chests .

It's still definitely luck.
I don't think they changed any of the drop rates because I feel like this is the same as before (from my own experiences).

Just keep on doing those expert maps and you'll find one soon!

Also, it might be worth pointing out that intermediate books are seen much more often in veteran maps and it might be worth your time farming for these instead since 8 of these equals 1 advanced book, in terms of essences.

Good luck!