ok, so I have the pro-comp Xterrians and they're cupped pretty bad.  I'm very good about rotating them, and keeping my alignment in check.  I was wondering though since the tires are directional and rotation is only front to back (and not the traditional rear pass to left driver, rear driver to front pass) if the directional tires are prone to wearing weird (not just the xterrians but the baja claw, etc). Any ideas?  

here's a photo of what I'm asking.  the red areas are where my tires have worn down faster than the rear areas of the lugs
 

A friend of mine has the XTerrains on his SuperDuty and they have worn really funny too, very similar to what you're showing... might just be an XTerrain thing...