Any one know what an Xt disc / 317/ db spokes wheelset weighs?
Would this be a half decent wheelset to use for aggresive XC riding (no freeriding)?
2 words: boat anchors
XT disc hubs are horribly heavy. The 317 rims thenselves aren't that bad, but combined with the XT disc hubs the package will be very heavy.
These wheels would definitely strong enough for XC riding, but you'll pay a huge penalty in weight.
If weight is your primary concern, look elsewhere. In fact, you might even consider custom wheels as they are not all that much more than stock (in some cases, cheaper).