Considering the Intoners other than Zero didn't get much screen time in Branch A of the main game resulting in them being pretty underdeveloped, I think this DLC is a good addition if you care to learn more about the characters and the overall story of this universe. While it's not a crazy big telling of One's backstory it gives pretty good insight into her thought process, who she is as a person, her beliefs and the things she cherishes and adores, and her reason for fighting in the first place.

It's a pretty cheap DLC all things considered so I think this is worth getting if you want to delve more into the characters.