I think a lot of people miss the point of carbon wheels and so do often end up with overly stiff wheel sets. When buying/building a carbon wheel you need to think differently. A 380g carbon rim is as strong, if not stronger than something like a flow, so you’re already buying into that strength from the outset. You need to build them with light spokes, preferably just 28 (24 for XC duties and even trail stuff if 24H hubs were easier to find). 32 is DH territory in carbon wheel terms, and brings added stiffness you just don’t need, let alone want. By reducing the weight of the spokes, and number of them, you add back in some compliance that you lose, but still get a set of wheels that will take a hell of a beating. You’re going to end up with a wheel that weighs probably 1400-1650 grams, but is as strong as something 500g heavier. Too many big thick spokes and it will just feel dead and too stiff, and you loose the weight savings – negating the point of going carbon at all.
Also I do agree that DH wheels aren’t that suited to carbon rims – for someone like Danny hart impact resistance is as important, if not more so than stiffness or weight. This is one weakness of the carbon rim, in such that while they will resist deflection amazingly, they wont give under huge edged impacts, they will just crush, often catastrophically (but not as often as you’d think I suspect). To get around this, you see massively beefy rims for DH, but thats now made the rim basically solid, and not that fun to ride, and offers little or no lateral or vertical compliance. I built some (ironically I guess given the above) for DH use only today, but I used Sapim Race double butted spokes, and only 32 of them – something that would normally be more of a trail build than DH, but I know the wheels will take it just fine, it didn’t need 36 straight gauge spokes like most alu DH wheels would run.