At first I thought it was IFS. I think IFS does unload more then a solid front axle naturally due to less unsprung weight but there are ways around it. I have seen other IFS vehicles not suffer from this like we do. I think of it this way, even with stiffer springs we have torsion bars. Torsion bars put weight on the crossmember that is attached to the frame not on the front like a coil sprung IFS like an FJ cruiser. So when you are on a hill physics play a role in that. Any vehicle climbing a hill will lose traction and weight on the front end but with torsion bars you already have weight placed on the center of the vehicle and now you are going to climb a hill you esentially have no weight on the front end. When I put a winch on the front it helped but I just feel there is no weight due to the torsion bars. Soft springs dont help either.
