Griffon nests use exactly the same exploration results chances that other lairs, so any differences are pure luck.
I really like to upgrade elephants & griffons after nature's revolt - and get heroic promotions for free.
Only thing I can think of to reduce spiders numbers is to remove lairs, but I would like not to do it. Unless you think it is broken as it is.
I have seen beasts, but no TumTum so far. But I do not play that much.
By the way, in the next patch I will include Xienwolf's fix that completly separates animals & barbarians (in spawning at least), also it makes animals spawn the entire game.
The farm problem is the most dire now, I do not know what the reason is. I try to find why AI likes cottages so much. It helps with research, but I am not sure if it is good in the long run. It was somehow changed it ffh 0.34 so it is in Orbi from 0.14.
I am going to improve plantations with a tech, I also thought of improving farms (possibility to get 3 extra food? but it can be broken)
I agree that yurt line is too good. I will check your suggestions. I am not sure about hills, as it stops all civs from building them on desert hills. Also, hills are supposed to be the best location for aduar, especially from flavor perspective (fortified town in a valley)
Quarries are required for salt also, not just marble. I think that mines might suit salt better, but I do not want to get rid of quarries.
How about quarry buildable everywhere. Or even limit mines to resource only improvement, and make quarry a basic mine improvement (with a possibility to discover all mineral resources, but no bonus from mine ones? - that will make you change quarry to mine when the resource is discovered). I always wandered what do they mine if there are no resources? Stone? If so, quarry it is.
Unfortunatelly, I do not think there is a way to make two techs discover one resource. So either pearls are for everyone (revealed with fishing perhaps) and lanun get another bonus (aquafarms? bonus for combat for ships?), or it stays as it is.
I am not sure I like the current implemetations of millers and prospectors? Maybe the current mechanics should be removed and another put in. That can be completly different mechanics. I thought of making guild-specific buildings provide bonus to discovery chance (the passive one), but so far no idea how to code it.
The other possibility is to up a discovery chance to 25%, and make prospecting & breeding require money (40 gold?). That would make it more predictable, reduce micro-menagement, also you would have to pay for the resource. I am not sure how would it work with Khazad, though, and they are supposed to be good at prospecting (reduced price plus a block to not let them cast it if they do not have enough money for the vaults?)