Warranty sounds like a ball ache. I've already been waiting 3 weeks for a 135 end cap from Mavic. Must all be watching Le Tour.
Looks like I'll end up with the Hopes and use these on the turbo.
Mavic wheels are pretty easy to service, even down to the bearings inside the freehub, so the other option is that you give it a go yourself.
There's lots of options for what causes the drag, but I'm pretty sure you would be able to locate the problem of you had a look inside.
Problem is a lots of customers never go fast enough to realised their wheels have a problem with the freehubs, luckily @yeahdext notice it.