I didn't get it until after tGS, but unfortunately Sevannah did speak for the Shaido until a new man returned from Rhuidean, and on top of that she declared herself a Wise One. I think either of these stations by itself wouldn't be good enough, but by combining both she made it difficult for the other Wise Ones to defy her without violating custom, and ji'e'toh isn't just "custom as strong as law," it IS law.

They did not just stand by and do nothing. Before Sevanna was taken by the Seanchan, Therava was seriously plotting against Sevannah. She asked Faile to spy on Sevannah and report back to her. She and the other Wise Ones sent a man (or men?) to Rhuidean so that if he survived he could immediately supplant her, and he was chosen by her rivals, so they must approve of the choices he would make as chief; primarily putting an end to all this nonsense. All the other Wise Ones wanted to return to the Three-Fold Land. IIRC they were really close to openly defying her when Perrin's raid arrived.

I agree that it seemed a little played out, but we hardly read about the Shaido at all until they captured Faile, and even then it was only a couple of chapters, the rest of the time they were just a distant threat on the horizon like all the others. And Rand did have to break the Aiel. It wasn't so overdone as to detract from the story, IMO.

Also, I think that when Sevannah convinced the others to kill one of their own Wise Ones, the countdown started on her own undoing. All the others seemed so horrified by what they had done that it was a tipping point.

No thoughts on the ter'angreal.