Buddhism spread to me. I went east in stead of west, these cities are production powerhouses. This advantage disappears however after some time, so I think I'll try to collapse the Han early on next time. They are the Rome of the east, it's hard to keep up with them. Stability should be fine I think, the economy rating compensates the territorial penalty easily. I think with this in mind, the Tocharians are OK for now.
I ran a test start as the Franks earlier today and they were the superpower, controlling entire China, Korea and the Samarkand region. Their cities were immense, a combined population of 6.4M. I don't think this is really bad, but the game still needs some improvements for this era. Very few civs were alive. Rome survived until the end of the 4th century, so that seems fine I think.