Having played the game about a quarter through, I can't shake the feeling they DID bite off more than they can chew. The game is solid, easily a B to Arkham City's A- (and I mean this in the conventional collegiate sense, not the skewed videogame sense where anything lower than a 90/100 means you failed and your employee's don't get paid).
They improved in the area of enemy variety and the boss-battles. The game's detective sequences do make you feel like an actual detective, even if they just boil down to "scan this thing and watch a video of the crime". They've also made the combat system more punishing, and tactical observation and judicious usage of gadgets and entry attacks is necessary to win fights - batman can no longer just enter a room and punch everything to death. However, in tightening up the combat system they've pulled several buggy flaws out of it that was covered up by the looseness Rocksteady's system had afforded it - often times slight variances in distance will cause combo's to fail or not follow up as they should, Batman will occasionally attack the wrong enemy, Batman's range has been reduced, sometimes you bug into terrain etc.
In fact, little niggling issues and bugs plague this game. I've already encountered a game breaker that will make it impossible for me to finish the Riddler side quests until it gets patched, because Batman cannot grapple-then-climb into vents due to clipping. This bug is exclusive to the PC version, I am led to understand.
More important though is a sense of style. Scan riddles are gone, replaced entirely with gadget puzzles ala the trophies of Arkham City. Gotham in general seems reduced in scope from Arkham city, it is packed with fewer nods to fans and despite the fact that criminals (and no civilians or cars) are everywhere, it feels empty and desolate. Pacing seems skewed, and over all the game feels like less of a Labor of Love than a product to be manufactured.
I suggest everyone buy and enjoy this game, because we can expect sequels at an increasing pace from here on out - and this is like as to be the last "stellar" example of an 'Arkham' style game until Rocksteady's next project (assuming the rumors about Silver Age Batman are true).