Well, I just read on the wiki...
"The 50% minimum autonomy limits Ming to only receiving half of the tax and manpower its provinces can provide, as the modifiers are additive, combined with the 15% penalty for different culture (but same group) and the 25% penalty from Chinese bureaucracy, Ming would often only receive 10% of the taxes and manpower from its most valuable provinces, like the Yangtze delta region."
Ming was very much playable, overpowered even back in 1.7. I could easily take on Russia or a Western power without Westernizing, and the faction system was actually useful. Now, Ming is nerfed to the ground and I have to rush to Westerners to save myself, killing the objective of uniting Asia. 10% tx and manpower from almost all my provinces? What a joke.