Thanks! I think it hasn't been discussed yet, but there's a problem with hordes and Ming. In the new patch, the AI builds a lot of forts (which is great and gives a challenge to the game), but this makes it very hard for AI hordes to succeed against a crumbling Ming in the middle of their disaster. This is why I think giving Ming negative fort defense modifiers in their disaster (both Ming Crisis and Unguarded Nomadic Frontier), or even tie it to low mandate malus, could help hordes to claim the Mandate. Speaking of which, I would also suggest giving special priority (ai factor) to AI hordes to invade Shun the second they spawn: right now, they will only choose to intervene in the event if they have a set of conditions met, but I think they should invade unless Manchu is bankrupt. This way, you "force" Manchu to attack Shun right when they form, which is the moment they are the weakest. Another thing that prevents Qing from forming is that Manchu does not have access to the Unify China CB (if you disable Mandate of Heaven DLC you have access to it). Maybe enabling it could help Manchu to form Qing in more games.
Finally, I have a question regarding Chinese Kingdoms. Are you planning on adding a decision to Chinese Kingdoms to restore the Mandate of Heaven if it has been dismantled? There exists already a decision to do so in the game, but it is currently disabled. Thanks again!