Don't take this the wrong way, but are you sure you are installing them right? I have 3-4 nut sets that I keep as spares because I thought they looked a little beat up, but they all look better than the pictures.
This is how I install;
No impact, do it all by hand.
*Install packed wheel bearings, and pack the space between the bearings with grease so when the outer bearing is installed, grease pushes through.
*Clean up spindle threads with a little brake parts cleaner on a rag.
*Inner nut on hand tight, using 4-post socket. This is hard to explain, but after replacing the D35 bearings numerous times, I got pretty good at "feeling" the sweet spot. I get a little rotational resistance, then rotate the hub both directions several turns while putting pressure on the socket, to fully seat the bearings. I then then back the nut off slightly. I might do this several times until it feels right.
*Note: The book says to torque inner nut to 35 foot pounds, rotate hub at least one full turn, back nut off 1/2 rotation, ret-torque inner nut to 16 foot pounds.
*Washer positioned so it will only allow the minimum slip of inner nut when torque applied to outer nut. This is the part that takes the most time for me.
*Put a couple of drops of medium strength thread locker on outer nut threads.
*Hand torque outer nut to 150 foot pounds. The washer and inner nut will turn slightly until the washer slot engages the tab and inner nut pin, providing the proper torque on the inner nut.
*Check bearing play with tire/wheel installed for better leverage.
This has worked for me for many years of trouble free off-roading, both with D35 and D44 axles. I got the thread locker idea from Winter, Paul B's fabricating wizard. I remove the outer nut with a impact to break the thread locker free, but do the install by hand.
If those are Warn nut sets, they have a life-time warranty. If you email their customer service, they will send you a new set.
Edit: When you have it apart, install a set of these in place of the spindle bearings and seal.
http://www.wildhorses4x4.com/product/Extreme_Spindle_Bushings_Dana30-44/bronco_Dana44