I had the same problem with my 1996 Pathfinder. I, like you chased after the sway by replacing the front struts, the rear shocks and having a four wheel alignment performed. I called my dealer to ask if they have seen similar ‘sway’ issues in other Pathfinders. From their response I gathered that this is a common problem with the Pathfinders. The fix for me was to replace 8 bushings in the rear suspension. Because these trucks have coil springs in the rear, they use upper and lower trailing arms (one upper and one lower on each side of the truck) to hold the rear axle under the truck. There is also a panhard bar, but I didn’t replace the bushings in it.
To have the dealer replace the bushings is a bit salty to say the least. The dealer will not replace the bushings. They will replace the entire control arm, 4 in all. I can’t remember the exact price, but I think that the upper arms were around $130 each and the lower arms were something like $170 each plus the labor to install them. I opted to buy the 8 bushings and install them myself. Each bushing was less than $20.
I will warn you that changing the bushings, although not complicated, is not an easy task. The bushings are a press fit into the control arm. A shop press of at least 20 tons is required to remove and install each bushing. I have access to a full machine shop so I was able to fabricate custom punches and holders for the control arms. Had I not had these holders and punches I would have likely bent the control arms and or destroyed the new bushings during their installation. I suspect that the dealer replaces the entire arm because it can be quite difficult and time consuming to remove the bushings and install new ones.
I hope that this was helpful.