I noted the camera to reinforce that there's very little difference, if any, between the way combat beyond AO enemies attacking more frequently. But to address enemy attack proximity: If enemies run up closer to Batman before attacking in AO than in AC, they still attack faster and more frequently than in AC, yet Batman's animations are largely taken wholesale from AC, meaning there inevitably is a move that had purpose in AC becomes less useful/useful in AO (i.e. aerial attack/aerial attack to other enemy, or using the smoke bomb). Enemies locked-on from further away in AA and AC, yet their attack speed was adjusted accordingly they also lost their lock-on to Batman easier, and regained it at a more reasonable pace. In AO, even if they run up closer to Batman before initiating attack, they're still locking on during other moves the player can't break out of or cancel, so rather than rewarding reflexes by making attacks faster/more frequent, it just changes a system that is already focused on managing large groups of myriad enemy attacks instead of moment to split-second-moment reaction. As good as the animations in these games can be, enemy attacks aren't animated in a way to support that kind of gameplay, as discussed in
this video (whole video is worth watching btw).
I mention Joker's Carnival because it's the hardest combat challenge in AC, yet it never breaks if anything, you beating it easily only supports the notion of how solid the mechanics are in AC. The enemies
do attack more frequently in that challenge than they do in the main game, yet you don't find attacks whiffing when they should've landed (like what happens in AO), nor do you have stuff like batarangs (which always auto-target to a degree) hitting armored enemies, breaking you combo (which happens in AO). It's completely fair and doesn't break unless the player messes up. AO messes up a lot (because of enemy attack frequency/speed, enemy-Batman animation balance, player lock-on, etc.) and is more about avoiding damage until you can abuse the electric gauntlets (or explosive gel + multi-ground takedown) rather than building a massive combo steadily having to manage different abilities (the only on of which that's broken being the bat-swarm).
AC and AO are extremely similar. I totally get how someone would enjoy one over the other. That doesn't change that AO does not objectively improve the gameplay over AC and it's a disservice to anyone related to the series (fans or developers alike) to dismiss AC's approach to combat the things AO changed
could've been objectively for the better. In a vacuum, they are better because they make combat more challenging at a lower level and on the surface. When taken into consideration in the grand scheme of things, those changes were implemented improperly.