Y'shtola is a Mary Sue.

[Zabuza]

I don't think burning years off your life works that way, getting tired due to it's effects. I mean if you really want to complain about a Mary Sue well Zenos

I disagree. Zenos has been shown to have great abilities true, but he has been shown to be an emotionally and mentally disturbed being. He has a gaping void in his heart that he doesn't know how to fill, and mistakenly thinks he can fill it by fighting us. He suffers from eternal boredom. He didn't care about putting a world through suffering to get what he wanted. He was not portrayed as a mentally stable individual.

If there is any mary sue like character in the story, it's purely the wol.

I agree with this, but the WoL represents the player. I find the WoL to be extremely boring as well, but I recognize the tricky balancing act being performed by having the WoL represent us. Go too far from neutral and you risk upsetting players. Heck, that even happened this expansion when the player didn't get the option to disagree with certain choices other characters made...