What has been mentioned to me and what I have noticed in the past is that higher ply rated, load range E tires are generally on vehicles that carry higher wait so the side wall defelection is stiff. At times these side walls take time to warm up and flex especially when left 35-40 psi and create a lope or vibration when driving. A light Jeep does not have the weight to work the tire, therfore never really illiminating the vibration. A bit lower pressure may actually allow tire to be smoother as the wait of the jeep may work on the tire, softening it and smoothing it out. Just got to play around and see what works for you I guess.
Always monitor air pressure against tire pressure as well as I assume you want to wear out the the whole tread width at the same time. Ride quality etc may suffer, as there needs to be a comprimize somewhere.
This is just my opinion, but i would never put 10 ply tires on a jeep. I assume the only reason anyone would do this is to have a stronger side wall for protection, but ride would definetly suffer.
For eg, I hate the ride of my loadrange E - 10 ply tires on my duramax. but due to payload, I have no choice. With a load on it is alot smoother. In no way does a street driven jeep need this so why do they put these tires on new? I would love to see a jeep dealers / manufactures answer. They may not vibrate new but I bet alot of them do after a while.