Can't say I really agree with you, I'd have to rewatch DKR though to freshen up, but what makes the movie salvageable is Gotham by the end being back to the same cycle of escalation and idolatry that caused the same problems as before. A sour ending, for sure, but a lesser movie would have made it all "a-ok" by the end, instead of just leaving Bruce with a happy ending.
As for Bane, I'm split on hating and loving the key moment where he becomes fake Bane: when Talia is revealed/hinted at, he his deflated like a hot air balloon and becomes just a goon that can be easily thrown around. even his words ring hollow afterwards.
It's not a as well thought up movie as Dark Knight, but for the sheer ambition of it I still quite enjoy it. That and both Joker and Bane were fantastic villains that struck a chord with people and an actual modern anxiety.