There are 13 creature mems, 1 boss and 3 biomes I need.
I do think 4 of them are just a waiting game but the other 9 are not possible for a reasonable person. Yes I'm not counting the known 3 that are not in the game.

1000s of delvs ago I needed one more then I do now. In the last 5000 delvs I've done I have not seen most of the ones I need at all. I do from floor 1 to floor 200 in private, public and challenge looking for the ones I need.
They are not in the game.
Yes I know people have them. Yes I know about mapping.
Why do some people have them and I dont? Delvs have been manipulated a few times since launch. We really have 0 clue where or if all of these are even in the game still.

I'm done looking. I gave 8 weeks of grinding 1000s of different delvs to get 0 progress. I don't even know where to look or go or grind for the last missing ones.

Since there is 0 way of getting the mastery in the game there is 0 point in buying packs.