With regards to the game, I don't have much to add beyond the posts from other people upthread. The writing was mostly excellent
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with The Joker being an obvious highlight, and Jason Todd still being a whiny dick a lowlight.
The biggest complaint I have isn't that the game is too large, per se. It's that the game seems to have been built by people who played Asylum and City to death really recently, and built on top of it. You know how any normal (decent) game builds over time, introducing new mechanics at the right pace so you've mastered the last one just as the next one comes along? To my mind the Batman games do that, but over the whole trilogy rather than within each game. The gadget/move list on starting City isn't far off where you ended up in Asylum, and the list at the start of Knight feels as complex as somewhere near the end of City, and then it gets more complicated from there. Maybe that's fine if you're a playtester who lived and breathed the games for months but I played them years ago and I've forgotten how they worked, so Knight was very close to overwhelming at first.
I was extremely glad I put it on Easy difficulty, which means I didn't have to sweat the brawling combat. That's where I have the least patience for the seventeen-dimensional game of rock-paper-scissors the game wants me to play, memorising which moves work on which enemy types. Predator combat, however, remains excellent, particularly once I'd reminded myself about the various tactical options of the various gadgets. I could see me doing some of the predator VR challenges.
There really are great new parts of the game mechanics in Knight, though. The sabotage gun is particularly good. I would have tremendous fun with it; sabotage the medic's healing kit, then hack a generator to explode and knock a guard out, then watch the medic get knocked out when he tries to revive the guard, and I'm laughing and laughing from the shadows. Fear takedowns are also great fun and even when it's a brawl against ten unarmed thugs they reward you taking your time to plan a stealthy approach and thin the herd before the fisticuffs start.