achilleszero
Emperor
What kills it for me is the fact that it has a bad drawback. It was unhealthiness which is easy to fix but now it's a revolution issue which isn't as easy... although that's more preference and playstyle I guess.
I'd like to see it be a positive without a negative (save the upkeep cost naturally.) I mean what's the downside to Caste System? Either make all of them have a drawback or none of them, you know?
Several civics in other categories have draw backs. Mercantilisma and State Property come to mind. Its not the drawback itself, its if the benefits outwiegh the drawback, that should be the concern. I never use serfdom, but some people do, and it fits some strategies well.