A prelude to a sequel, not a pre-sequel
As a promotional tool, Borderlands 2: Commander Lilith and the Fight for Sanctuary isn't bad; it's perfectly playable and has some fun moments. As a game, though, it's fairly bland and feels unnecessary to the franchise.
The Fight for Sanctuary picks up after the events of both Borderlands 2 and Tales from the Borderlands, explicitly to set the stage for the upcoming Borderlands 3. But it doesn't do a hell of a lot of foreshadowing for the next game -- and it doesn't have much story of its own to tell, either. Mostly, this DLC is a recap to reacquaint years-lapsed Borderlands players with Pandora's wacky cast of characters.
And while it's fun to watch Tiny Tina fangirl out about a big missile, the cast overall is glossed over pretty quickly. Between Lilith, Mordecai, Brick, Vaughn, Moxxi, Ellie (sorry Scooter), Mordecai's new pet Talon, Tina, Dr. Zed, Marcus, Crazy Earl... most characters only have about a minute of screen-time, and barely get past re-introducing themselves.
Vaughn comes the closest to providing real entertainment, with some bandit-ey mission text and radio banter, but he falls short of Shade from Captain Scarlett and Her Pirate's Booty. Even this DLC's antagonist is a flat villain with minimal (and uninteresting) backstory, and ultimately defeating him isn't very satisfying.
Something that this DLC does execute well is a new item rarity, the "effervescent" tier. Like Legendary items, these are more scripted than random, and their effects are bonkers -- like an assault rifle that shoots 10 bullets at once, or an SMG that you can throw away as it spins and shoots in all directions. Effervescent items are also crazy-sparkley, which is a very cool visual effect.
So, I look forward to more effervescent items in the late game of Borderlands 3.
That said, while this DLC pack isn't "bad," it doesn't really feel worthwhile either. The whole thing could have been replaced with a 15-second cutscene in the beginning of the next game.
Better than: Borderlands 2: How Marcus Saved Mercenary Day
Not as good as: Borderlands 2: The Horrible Hunger of the Ravenous Wattle Gobbler
Oh yeah: where's Torgue!? He'd better be coming back!