I think the root of Siuan's problem was that she grew up in Tear which has to be one of the most oppressive societies in the Westlands. The High Lords rule with a capital R. Anyone lower down in the food chain does what he or she is told by her superiours or else. Siuan would not have had access to the top ranks of the nobility to realise that they play the game of houses among themselves.

Next she is sent to Tar Valon where as novice and accepted you jump with a sister says jump and you don't ask questions when it comes to the important things.

As soon as she becomes Aes Sedai she is taken in charge by the Blue for her new role as future spymistress and from New Spring it seemed that she was being tightly controled. Again the leason she would have learned is that while you might bitch about the boss a bit when a real order came down you did what you were told.

Finally she becomes Amyrlin and I think that while she may have rationally known that the Hall and Sitters had to be kept on side unconsciously she was of the mindset that she was the boss and when she gave orders the Hall and the rank and file Aes Sedai should obey. Perhaps she was not as extreme in her views as Elaida became but even by TGH there are signs she has very little influence over the politics in the Hall.

Moiraine would probably have made a better Amyrlin. Growing up among the shifting alliances of the noble houses of Cairhain she would had it instilled into her that one needs to put one's enemies on the back foot and keep one's allies happy and allied.

Siuan's intentions were good but then one might say Elaida's were as well both both women went about their goals in the wrong way.
As for Leane she had loyalty to her friend but I wonder is the Keeper suppost to inform on the Amyrin if she startes to skirt the law.

My understanding was that the Keeper was the mouthpiece of the Amyrlin and suppost to be her chief of staff. Having her spill on her boss would be a bit like having a US secret agent on protection duty for the president telling the first lady her husband was having an affair. They are there to do a job not to go running to tell the world about any scandle they come across.