Yet she sure acts like she is the head of the city by throwing herself and everyone else into a war with sebastian. If the captain of the guard is not the leader of Kirkwall then who is? Kirlwall is a city-state and have no Banns. The Viscount is in charge but is gone, the Knight Commander and the Templars are gone or turned to red Temps. Kirkwall is pretty much under the martial law of the city guard. She is in charge.
Bran is provisional Viscount but at this point in time, with the threat of war, the Guard-Captain has the authority to conscript from the populace. With the threat to the city -- and even before then -- she and he have the authority to do a lot, though obviously you have to account for the nobility -- whom, let's be honest, one has to expect to act like petulant children.
Aveline, I'm not sure I know how "incompetent" she is. It seems that the citizens of Kirkwall were liking their new city guard just fine. If it's good enough for them, it's good enough for me.
It's mostly in her attitude. From failing to secure a site where Demons popped up after someone was seen fleeing from the scene of the crime -- which Hawke can relay to Emeric -- to her lack of an investigation into the guardsmen accused of raping an Elf in the Alienage. She should take such things seriously, considering that they 1) reflect poorly on the Guard and 2) are a lingering part of the corruption the Guard had to face.
But then, what do the lives of Elves matter? No one gives them much thought. And indeed, much as she would deny it, she is technically corrupt. She has altered guard patrols to protect her friends, bent the law to get them out of jail, etc.
That's why I said that although she's probably one of the best Guard-Captains Kirkwall has had, that is not saying a whole lot.
As for Sebastian, my problem is less that he doesn't kill Anders when he has the opportunity, and more that his first reaction is to tell Hawke to kill him, instead of at least trying something himself. The same way he wanted Fenris to turn over Anders and Merrill to the Templars instead of doing it. The same way he waited in Kirkwall that someone kills his family killers for him. I see a deplorable pattern here, that's all. So yes, I think he's a coward because he doesn't have the courage of his convictions when he doesn't have buddies to back him up.
I agree with all except for the family killers one.
He's one man and you'd expect him to go up against an entire mercenary company on his own? That's not acting on convictions, that's suicidal idiocy. If what you're saying is he should've joined Hawke, I suppose I could agree.
Though Hawke would've first had to tell him. Sebastian didn't even think the bounty was left up there when we inform him of the deed.
and this next bit isn't necessarily directed at you, though it does work in conjunction with your post.
To be honest I don't care much for how Anders is executed in the main game, and it's one of the things I rewrite for my headcanon. He's turned over to the Guards of Kirkwall there and is given a full trial (for however much it's worth) wherein he pleads guilty and walks the gallows.... funnily enough, at the Gallows, before as many people as wished to attend.