izigame.me

tl;dr If you enjoy strategising with the existing roster and are comfortable with the game's difficult learning curve, then you'll get a lot of fun out of the DLC. Watch out for a bit of grind to unlock the Crusader.
Good stuff:
Highly recommend Duelist. She's probably Red Hook's most in-depth character in the franchise, and rewards you greatly for planning and being creative with how you play her. She embodies the high-risk-high-reward playstyle, enabling and demanding a lot of clever tactics and decision and feeling smooth and fluid while doing so. It's one of those cases where you can be sitting there thinking over all 5 of her abilities to use at any given turn.
Crusader is nice. If you're familiar with him from the first game, he maintains a pretty similar identity in terms of gameplay. Personally I think he suffers a little from some of his skills struggling to compete with others which makes his effective gameplay a little flatter, but that might change with balancing / I might just be bad at him lol.
He's a lot simpler than Duelist but that's not an inherently bad thing. He does better as an enabler of his team rather than having so many big fight swinging big brain plays of his own, which in turn makes gameplay with the existing roster (and Duelist) more enjoyable.
Bad stuff:
The same depth that makes Duelist engaging can also be frustrating. She's a challenging character and will likewise punish you for poor play, and that can make for a bad experience especially if it's not immediately apparent as to why the choice you made didn't work out. You might not have bought and played DD2 for the deep "sit there and strategise" kind of play, which is very reasonable. She may be more appealing if you get more familiar with DD2, and are at a point of comfort playing that the challenge of her design is more welcome.
As others have noted, Crusader is locked behind a fairly lengthy (at least a couple hours) in game quest. People are understandably dissatisfied to have content locked away for that time despite paying for it. The gameplay of the quest itself can also be a little flat. The new enemy faction, the Military, shows up in unique enemy mashups on the road. Their signature gimmick are their barricades, which are somewhat hostile to strategy. They are resistant to a lot of things and they guard their team. Means to play around guards are rare, hence the main strategy of these fights is spamming shit till it breaks, which can drag out. The enemies and the new boss suffer from the same problem to a lesser degree, i.e. being resistant to a lot of things and not allowing a lot of room for fun strategies unique to them. Their occurence is also down to RNG, which means finding them for the quest and how much / little you want to engage with them outside of the quest isn't in your control.

Overall I think it's worth, but you should consider the value this game brings you already before you decide to buy. If you appreciate DD2 from more of a distance than I do, then you might want to think on it. But if you like the art and the gameplay loop and the strategy and the characters, then this DLC is a no-brainer. Plus, the new characters are hot!