A ... small matter.
My understanding of the Arkham Knight DLC situation had been that, while most of its "story" packs were in the same neighborhood as the Harley Quinn pre-order bonus - which I previously described as a "pretty baffling disappointment" - the Batgirl-centered A Matter of Family was much more substantial and worthwhile.
That turns out to be a half-truth. The "more" part is true; not the "much" part.
A Matter of Family is set some time prior to The Killing Joke, and starts with a flimsy excuse to set Batgirl and Robin up against the Joker sans Batman. (Joker claims that he'll kill Jim Gordon if Batman shows up. Since when would that stop the Bat?) The map is open, but miniature -- Seagate Amusement Park is an artificial island isolated from the rest of Gotham, and its size feels comparable to one section of Arkham Asylum's overworld.
After the DLC's intro, you're tasked with rescuing three groups of hostages. While the map's openness means that you can go after these groups in any order -- after the first and second rescues, there is a non-optional objective to defuse a bomb at a specific location; then after the third rescue, a boss fight. So aside from picking which hostage to rescue first, the mission is intensely linear. And the whole affair is like, one or two hours long, maybe another if you seek out the optional collectibles (which I didn't).
Batgirl's moves and gadgets are all the same as Batman's, but fewer. The only "new" ability here is that some hackable objectives and traps don't require a password, that is, using the hacking gadget just finishes the hack automatically. Yes, that is a vanishingly minor distinction from Batman's kit.
A Matter of Family "works" in the sense that it delivers some of the same great stealth and combat fundamentals as Arkham Knight. Otherwise, this DLC pack is shallow, un-innovative, and utterly uncompelling. It's got more meat to it than the other story packs, but ... that's a pretty low bar to clear.
Better than: Batman: Arkham Knight - Harley Quinn Story Pack
Not as good as: Batman: Arkham City - Harley Quinn's Revenge
I kinda can't believe: that Batman: Arkham Origins - Cold, Cold Heart ended up being the best standalone Batman episode.