Generally like them. Siuan a bit more than Leane because she has a more important supporting role in the overall plot. Of the three mentor AS characters (Moiraine, Cadsuane, and Siuan), she's probably my favorite.

Siuan knew she had a good chance of getting stilled, and she was even willing to accept it, but she really did get shafted by events. Being too secretive and controlling didn't help. However, she had damn good reason to be secretive, she knew the BA was active, she knew they were a threat to the DR, and she knew that they had taken out Tamra Ospenya and likely Tamra's searchers.

It didn't help that Rand proved to be far more difficult to handle than anticipated. Moiraine messed things up in the beginning by making Rand suspicious of her, and Ishy was more than happy to muddy the waters further. So Rand got into the position where he didn't trust the AS and feared they were trying to use him. As a powerful ta'veren,, he was even more difficult to control.

Of course the real problem was the Elaida didn't take down Siuan because it was the right thing to do, because Siuan broke the rules, didn't consult the Hall properly, because she was a bully or any of that. She did it because she didn't like Siuan, and because the Red Ajah was still looking holding a grudge against the Blue over Bonwhin. Even worse, Elaida was being used by the BA to sow chaos within the WT itself; the whole Red-Blue conflict was an excellent opportunity for them to exploit and they did so on both sides. So what happened to Siuan was not a matter of WT justice, it was a combination of Red thickheadedness and plotting by the followers of the DO.