Slitherine

Just finished a MP game of Pirates V Ming and found the Pirates to be invincible, they squashed the Ming with little loss.
On completion I noticed that there were 21000 Pirates and 16000 Ming, seems a huge difference in numbers.
Question is " are the Wokou Pirates too cheap " ?

I have beaten Wokou in MP before, but it's always a nailbiter, never a +25% win. Cavalry is key, and cheap light artillery is helpful too. They also have trouble dealing with skirmishers, as they lack horse. But, if you roll Ming vs Wokou on a map with difficult cav terrain, you're pretty much totally screwed.

Why are they all impact foot anyway? Weren't they just small bands of raiders that went around pillaging villages till the sluggish behemoth of the Ming army finally came to take care of them, if they didn't leave already?

That is a very good question that has not been answered yet.
Any chance of an answer from the Rule Writers/Jomni ?

They have the reputation of conducting fierce charges.

One thing to note, since we are fielding large armies of thousands of men in the game, the Wokou army ends up having a lot more men than historical due to the points system. This in turn sort of enhances their effectiveness. But individual units are actually not too good.