Black Hand Robe. I actually like both versions of the Black Hand robe. I think, if you were to, say, boost the brightness/contrast on the first version the details would probably show up better. At any rate, I think the first version is well worth keeping. The brighter version looks very nice, though (to my eye) the dark portions of the robe (sleeves and skirt) look slightly flat. I think that portion might benefit from adding more detail.
Wizard Robe. I think at least the black area of the belt could be lighten a tiny bit, as you say. But I wouldn't lighten it too much. One of the things that makes this robe really eye-catching, in my opinion, is the contrast between the belt and robe. I would leave the brown and gold portions of the belt alone and just lighten the black in the middle.
Dark Wizard Robe. This has a lot of potential but I think there's not quite enough detail to make the robe stand out yet. I think the quilting ought to be made more apparent. I'm thinking out loud here, but maybe try very thin gold thread to define the squares - nothing flashy, just a slight highlight of gold to emphasize the patterns. I think the very dark brown section under the belt might be made brighter or even whiter to contrast with the black in the rest of the robe (basically the opposite of the contrast in the Wizard robe).
Conjurer Robe. I think the red and gold colors work very well and the pattern is nice. To my eye, the black in the armored pieces draw too much attention to themselves. I wonder, what would it look like if you were to make those parts a bit more red to blend in with the red in the cloth? (It's very hard to judge how these thing will look without actually seeing them on an NPC in the game, so maybe the stark black-and-red contrast may look different in-game, I don't know. This may be one of those things I'd get used to once I saw them a few times.)
Leather, Mithril. I'm actually partial to the Leather myself. I wouldn't change a thing on that. Actually, I wouldn't change a thing on the Mithril either. I think both robes are excellent as they are.
War Priest Robe. I love this. Really, I think this is superb. I wouldn't change a thing on this robe. A great job - really, really nice.
Daedric Robe. If I had any suggestion to make it would be to add a bit more detail to the skirt. I think all of the rest of the robe is great.
As to what Oscuro NPCs should get robes, my vote would be to put robes on Amazon Raging Priestesses or Amazon Wise Mothers. They are mainly Mages, if memory serves, and it could be a sign of status to not have to wear bikinis or go naked, lol.