Just finished my rewatch of both seasons of Darker Than Black + the interquel OVAs. Revisiting this series a decade later it still remains one of my favorite anime shows and sci-fi settings, and I still enjoy how colorful and varied the art style is. Not to One Piece levels of exaggeration of course, but pretty much every character with a name, and even many who don't, have an instantly recognizable and distinct look without falling into caricature (mostly). That's good character design.
I can report that the second season, Gemini of the Meteor, is far, far less disorienting if you watch the interquel OVA beforehand to provide the context on why and how Hei and Yin are in the situations that they are. And the plot isn't as confusing as I remember it being but the ending is still confusing on first blush and overall very obtuse. I think it would've helped a lot if the pacing had been tightened up a bit earlier in the series. After Hei and Suou's group reach Sapporo the show spends 25% of its runtime there spinning its wheels on the Norio subplot and I'm confident that you can cut that arc down by half without losing any important information and that way you can give the rest of the cast and the rapid-fire reveals at the end of the show more breathing room. As it is the final episode asks the viewer to hand-wave a lot away through setting-related weirdness which is "okay" since the first season asked you to do the same but it didn't have to be that way. As it stands my favorite part of the second season's ending was when Kirihara's Golgo 13-ass-looking boss randomly showed up during the credits looking exactly like Duke Togo complete with assault rifle and shredded clothing.
The first season is still great noir sci-fi, the second I think I like it a little more than I did when I first watched it now that I actually "get" it (?), but I don't blame anyone who hated it since the storytelling did it no favors and I doubt it was what fans expected or wanted from a follow up. The real tragedy though, was losing Yoko Kanno.