I didn't think it was possible, but this DLC retroactively made my opinion of the base game worse. It's that bad. I don't recommend buying it even if it has a huge discount. In fact, don't play it even if someone gives it to you for free.
For starters, this DLC gives you the middle finger in your face if you chose to complete all or most of the stuff there is to do in the main game. For whatever reason, the developers thought it was a good idea that you couldn't inherit ANYTHING. You get some bonuses based on what things you completed but it's nothing compared to everything you lose access to when you move from a completed Tales of Arise file to playing Beyond the Dawn. You don't get to keep your lvl100, you don't get to keep any gear (losing your custom accessories sucks the most), and you lose nearly every single artifact (which means you level up slower and you lose a bunch of convenience things like longer cooking effect duration).
As if that weren't enough, the game also artificially slows down your progress and dangles the things you lost right in front of you, putting them right out of reach. A bunch of useful artifacts are on the Training Ground fights but you just don't have the level to do them until you're 2/3 done with the expansion. You can start with all the lures and fishing rods but you can't fish anything useful; you even start next to a fishing spot in Adan Lake, but the devs went out of their way to REMOVE the boss fish, just so that you can't cook Fish Steak and earn exp faster. Right at the end of the expansion you get back the Devil Arms, but they're useless because kills don't carry over from the main story and the expansion is too short to rack up kills. You have to re-learn a bunch of artes because you lose a bunch of proficiency and most of your title skills get unlearned. All of these things put together make one of the few enjoyable parts of the game (combat) feel way worse.
Also, I hope you like tutorials, because the DLC forces you to re-watch most of the tutorials that you already saw in the main story even though realistically no one is playing the DLC without having first completed the main story. You also have to see the animation for picking up an item for the first time even if you already picked it up in the base game. The whole thing is structured as if Beyond the Dawn were your first experience with Tales of Arise instead of the main story, which is a baffling decision.
The writing is somehow even weaker than in the main story. The characters are almost all one-note and are defined by gimmicks instead of having actual personalities. One of the few things I liked about about the main story was Shionne's character development, but she's pretty much done by the end of the base game and Beyond the Dawn doesn't add anything interesting to her character. Alphen is as frustrating to hear talk as always; he's always second guessing himself, blames himself for every little thing that goes wrong in the world, and always downplays his own achievements. The new character (Nazamil) could almost have been interesting, but Beyond the Dawn blazes through the story, gives her very little time to develop, and about halfway through the expansion she goes completely off the rails.
The worst part of the story is that, thinking of how the worlds unite at the end of the main story and how a certain character's motivation is to create a world where everyone is equal and there is no discrimination, Beyond the Dawn made me realize that the premise of Tales of Arise is just a significantly inferior version of Tales of Symphonia. Given all of the other problems this game has I pretty much handwaved the fact that it's never explained why Dahna and Rena were supposed to be a single world in the first place, but I just can't overlook how the main antagonist of Beyond the Dawn feels like poorly written Mithos Ygdrassil.
Although this is almost a nitpick compared to the major issues of the expansion, the sidequests aren't fun to do either. They're just more fetch quests and extermination missions. They do add more dialogue, but I already made it fairly clear what I think of the writing. Needless to say, I skipped most of it.
It took me 9 hours to complete the story and another 4 hours to grind out all 40 of the sidequests. Some would say that it's not worth it to pay 80% of the price of the base game for an expansion that is not even 20% as long. Me? I'm happy it was short. 30 minutes into the DLC I already wanted to drop it.
I knew about the main problems of Beyond the Dawn based on other reviews, and despite that it still managed to disappoint me. The only reason I still bought it is because I wanted to get all the achievements in Tales of Arise and around 11 of them are locked behind this DLC. If you're not a completion obsessed maniac like me, do NOT buy this DLC.
I hope that Namco seriously rethinks their way of approaching Tales games, because if this becomes a trend going forward I think that I'm never touching a new Tales game again, which is a massive disappointment because I grew up with the absolute banger that is Tales of Symphonia and I loved their previous titles.