What I love is the sneaky way they assemble elements over time, just a little bit here and a little bit there, until the bigger picture emerges. So it's easy to be overly critical of a given episode.
Like with the "boring" political episodes earlier this season, which established that the Republic did have a problem with corruption (showing us, not just talking about it), which was necessary setup for the new notion of Separatists with legitimate grievances, which makes the main characters look less stupid for not being suspicious of a war that has no apparent cause (it does have a natural cause, now) and possibly is going other interesting places in the future.
For instance: why wouldn't Anakin see the same corruption problem the Seppys did, yet come up with a different "solution": an Empire that can crush the corrupt elements far better than a weak and divided Republic? And presto, the political side of Anakin's fall suddenly makes sense. He doesn't even need to be apolitical and naive, which has been my assumption so far, and the story can still work just fine.
He can have intelligently reasoned and "legitimate" political viewpoints that make him distrustful of democracy. In his experience, democracy simply doesn't work. We can't extrapolate our own viewpoints to him, or his situation. There's no law that says that all sci fi has to be some kind of metaphor for modern-day Earth.
So what might be the purpose of the Nightsisters arc? Well, we've established that Sith aren't all bad. Dooku and Ventress had a loyal, affectionate relationship. Ventress probably wouldn't be so angry if she weren't feeling massively betrayed by someone she trusted implicitly. She seems to be intelligent, yet it never once crossed her mind that Sidious might ferret out her secret apprenticeship and demand that Dooku kill her, and that Dooku might comply. If she thought about it at all, she probably assumed that that would be the trigger for her and Dooku to usurp Sidious.
That shows more complexity for the Sith that pushes them incrementally out of cardboard-villain status, which is going to be vital for Anakin's story. He's not a cardboard character now, so it's not reasonable that he can become one. If we see the complexity in any Sith character, we can extrapolate that to Anakin.
I'd like more details about Ventress' backstory. Dooku offered to train her in the Dark Side, but why did she accept? What is the difference between a Jedi who accepts something like that, and one who doesn't? The details will be different for everyone, but there has to be some commonalities, and their common history of being torn from their loving family can't be it, because that happens to all of them. Does it simply come down to personality quirks that are like cracks in the facade that let the "darkness" in, and after that, it's a snowball effect?
