well buddy, i am so sorry about nobody paying any attention that I will answer you myself.
The problem is that I dont know as much as i would like, and I am a begginer.
I dont know about cob, but in Los Pueblos mancomunados del estado de Oaxaca, en México, there a lot of houses made of adobe and those can withstand months of humid climate. It rains (there) a quarter a year and is humid enough to have fog another six months.
They dont plaster the adobes, and the basement is always humid (the roof is not that big. I think they endure when the rain hits the walls diagonally and not directly from above.
The reason they withstand maybe that they use donkey dung or agua de nixtamal, I am nopt really sure.
If you still there, maybe i can send you a couple videos related to this matter.
