>>81486502You can access the DLC at chapter 9 (out of 11) of the base game. It's 5 chapters long.
It's harder than anything in the base game, so you might want to do it after beating the base game, before starting NG+.
Although there is an argument for doing the DLC as soon as you get access to it so you don't miss a few new voice lines in the base game.
It being harder than the base game means that if you are rusty, you might want to play though a new game just to get some practice. That's what I did. That, and my save was NG+. I was getting 2-hit killed. Not the best to jump straight into.
It's not stand-alone. It's set in the past and expands on all the central characters. Especially those immediately related to Carlo.
I said it was very good. But that's not to say it's perfect. The first boss has camera issues and the second last boss is a little BS.
Some of the most kino boss fights in the game. Levels are good, generally less linear than the base game.
I love the narrative.
All the new weapons and legion arms are good.
My favourite record: https://www.youtube.com/watch?v=S6YWEDA3wNE