in my experience, since the dlc came out (and i don't own it) i feel like ming collapses less often than it did before. before it almost felt like 90% chance it would happen, now it seems 40% or so. because i don't have the mandate dlc i can't say for how ming is now, but you definitely can't exploit their mandate, so they can neither become super weak as can be done with the dlc, but also cannot get strengthened via tributes and mandate reforms.