Finished chapter 3, this one actually had the biggest changes.
I'm not sure if the original chapter three was hated or something, but it almost seems like they want you to go through it as fast as possible now.
in NG2 this area is FILLED with fiends, they are just fucking everywhere and show up by the dozens, there are also tons of archers to make your life miserable.
in black the fiends are replaced by ninja dogs and claw spider ninjas; they only show up twice, once before going into the underground, and in the underground itself in that one long passage, they are just as relentless with their grabs and attacks as in NG2 though, but there are less of them and only two encounters.
Then there's entire corridors that are just empty now, like when you have to destroy the fans, nothing happens there, in NG2 it's filled with every enemy type, archers, ninjas, claws, fiends.
They also blocked off the two extra passages you can find by destroying the fans, so there's nothing to do in that area now, not even finding the incendiary shurikens (I guess they are removed entirely now? I don't remember if they were removed in sigma), you just destroy the fans and move on to the next area.
The boss of this area is complete trash in NG2, and while he still sucks in black, he's a less annoying now thanks to being able to lock on to his head with the bow.
So while the enemies are just as aggressive as in the original, this section of the game is actually drastically easier simply because all the fiends are gone and the projectile spam is lessened.