I think for me the problem is that their endgame and final act was simply to blow up Gotham, except knowing that seems to invalidate all the hustle and blustle Bane goes through.
And I don't even want to pick at Talia's rationale since (if I remember the film right) she's destroying Gotham to avenge her father............a father she doesn't even seem to show much affection for because of what he did in her past. She doesn't even have his belief in burning Gotham to cleanse it and allow a rebuild. She just wants to blow it up.
They seem to have no real plan for afterwards. At least R'as had something in mind.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist