I was going to say that Zhu Jiu is very much the moustache-twirling villain, but on second thoughts, I think in fact his loyalty to Ye Zun helps him to transcend that a bit, maybe?
I'm never sure where to put Zhu Jiu! (I only find him even slightly interesting when he starts being all frail and vulnerable, but I think you're right that his loyalty and especially his ending scene go a bit beyond the villain stereotype.)

I wonder how useful it is to have them be aware of their own flaws and trying to improve, versus falling into them over and over without realising.
That's a very good point (and not an obvious one). I think my protagonists are to some extent forced by the narrative into recognizing their flaws--privilege, self-deprecation, passivity--and dealing with them to some extent, but I'm not sure yet where any of them are going to end up, oh dear :)