This happens to be something I've got a lot of experience in.
I'd say your reference sheets are comprehensive enough - they ensure a good amount of detail.
I think the characters aren't too cluttered or under-designed, but they could benefit from a little more consideration into their clothing. I feel like Flare's shoes might need a bit more thought, and Shade's whole outfit too. As you showed the layers to Flare's clothing it would be good to pay more attention to how Shade's clothes work. Is his shirt all one thing or is it layered? Are his sleeves attached to the shirt or not?
I'd also recommend making their outfits as practical as they are decorative - they definitely suit the aesthetic and mood of the story and genre, but maybe it could be a little clearer what they do, based on design? For example, I get the impression Shade is meant to be a warrior of sorts, but his outfit doesn't read as the most practical for a warrior. Perhaps he should have more armour pads, and other soldier iconography? If he's not a warrior, perhaps something else to indicate what he does? If he's wearing an armour chest plate, perhaps it could be shaped a bit more convincingly? He definitely portrays a stoic look very effectively with his cool colour palette and low saturation.
I get the impression that Flare is a rogue of sorts, or something like that... but I don't get much of an idea of her personality. She's obviously got an intimidating streak, but perhaps showing more of her personality traits in her look would help her stand out more. She has a lot of culture in what she's wearing, but you might want to give her a distinctive stance or mannerism, or some slightly more exaggerated shapes.
I'd say you're certainly learning a lot of good techniques for character design, but there are just a few more things to bear in mind. That's my two cents for now, and I hope it helps!
