my Friend has a pro comp lift and it is VERY stiff im not sure if it is your jeep that is the problem or your suspension but all the guys i know who like going to the dunes in there jeeps have a procomp lift and they sail there jeeps. you might be able to soften it up if you take out one of the bottom leafs. that or you order the wrong suspension.
Next time you get a wheel in the air stop and look for things binding up. and check the amount of travel you get with your shocks. they might be limiting you as well