Sure this comes as old, but these still get read, so I may as well post my thoughts here. I really haven't played China... but, I would expect the article here has hit the nail right on the head about them having faster military production than most tribes. I think it really even goes further than this. Any industrious tribe can plant, chop forests, and then re-work/work those tiles faster than other tribes. So, have a corrupt area, but really need an extra rider or defensive unit or even an artillery? Plant and chop and you'll get it fairly quickly. And, I think there's even something more to China.
For those familar with Moonsinger's excellent "effective use of artillery" article, you'll know it relies on three things working in combination really
1. Settler placement properly near a town you want to take or raze with a few defensive units.
2. Artillery proper.
3. 3 movement *units*.... to minimize losses
Now, her article comes as intended for upper levels mostly or games you really want to pick things up for whatever reason. So, it talks about artillery and cavalry vs. infrantry. But... say you don't have saltpeter and you've played as China (maybe that's an interesting variant... no saltpeter allowed as China), but you've got horses and iron. Say you also even enter the industrial ages at about the same time as the AIs. The AIs often will ignore the Steam Power-Electricity-Replacable Parts path for a bit, paritally since they ignore Electricity somewhat and don't see Replacable Parts. So, if you beeline to Replacable Parts (maybe even forget Industrialization) and you play as China, then you would have riders, artillery proper, and hopefully infantry as defensive units vs. rifles. That should make for a not too bad war even with a fairly fast tech pace whereby you can acquire saltpeter, or pummel an AI or two so that they don't have rubber or to death. Through in easy promotions to elites and I wonder about how well China can warmonger throughout the entire industrial age without any saltpeter whatsoever.