Why so serious?
Hmm yeah, I think that arc is the best too. Everything around the torture still is my favourite scene and besides being well written the arc obviously turned everything upside down. Don't really agree with Kaneki being super lame/boring before, but there's no doubt that he's turned into a more multi-layered and badass/crazy character.
The whole Kanou hunting is one arc to me (which certainly is more action-focused) but afterwards we get like 20 chapters with hardly any action. Rize/Kaneki confrontation, Hide meets Touka/Touka meets Kaneki, Juuzo backstory, more Amon and Akira characterization, Takasugi Sen (with all the things she reveals to Amon), etc.
I guess the last arc stands out so much, but to me all those things mentioned above were great, it's those stories and interactions where I feel like Ishida really knows what he's doing.
Attack on Anteiku (that's what I call it xD) was really good in my opinion. Sure a connection to most characters was missing but then again, it's not like the Anteiku staffers outside of Yomo and Nishiki + Touka/Kaneki ever got much screentime, so they were not necessarily boring but never had the time to grow on someone. IIRC that's only a really small part of the battle though, most is focusing on Yoshimura/Doves, Kaneki/Amon, One Eyed Owl(King)/Arima. Considering that I really cared for Yoshimura, Kaneki and Amon that arc was pretty great to me overall, not to mention everything that happened.
Like you said, isn't that Amon/Kaneki conversation something you wanted? XD I think everyone wanted that, but reality doesn't work like that and would've made no sense in such a desperate situation anyway. Remember the first chapter? It was Kaneki who said that a story with him in the lead role would certainly be a tragedy, and that's what we got. I was pretty sad but you have to applaud Ishida for his balls, considering the "good" guys lost completely. Just like you I was really surprised too, I don't think anyone expected things to turn out that bad.
That being said, did you read the "Kaneki = Haise ?" thread? Feels like you didn't, there are a lot of hints/proof gathered there. Not sure what makes you think that Amon is dead for good? Lots of people are speculating when he will return, we never saw him die for real. Quite a few suspect that he was used in an experiment with Yoshimura and that he's a ghoul now too (basically opposite sides this time, with Kaneki/Haise working for CCG and Amon for the Ghoul side somehow).
What are your thoughts about Takasugi Sen? (The Novel writer Kaneki admired, who reveals all that stuff to Amon)