In my career as an equipment salesman I have put an awfull lot of miles on dirt and gravel roads, combined with heavy towing of equipment and then the regular farm duties of the truck as well.
I have had the best luck with BF Goodrich Rugged Trails and have put 75,000 miles on a few sets.
These would be E rated 10 ply tires on a 3/4 ton Dodge. I have found them to be the lowest cost per mile, but they do not necesarily have the greatest off road traction, I would call them a multi purpose tire.
I have noticed some rugged trails have a tendency to develop checking and cracks on the sidewalls over time but I have never had a problem with one failing.
Several years ago I had a Goodyear Wrangler 10 ply seperate the tread from the casing and wrap around the axle and made control of the vehicle "interesting" for a few seconds.
The flapping tread did about $5,000 dammage to the side of the truck and just missed the fuel tank.
When I got the truck stopped it still had almost 80 lbs of air pressure in the tire.
So I haven't bought any Goodyears since!
I've also tried Pirelli tires and found the traction to be poor and that they did not last nearly as long as the BFG's.
I'm due for a set of tires anytime, it will probably be another set of BFG.