Sounds dumb but check that everything up there is well lubed. I had DW with my 31's, went through all the same stuff as you, kept going back to discount tire for balance, rebalance, road force balance, etc. Nothing loose underneath. Then realized the lube points were being neglected as a part of the dealership $45 oil/lube visits. Lube'd it up and it made all the difference. Now just have a slight shimmy (cam bolts are next). Switched my 33's back on and the shimmy is now almost completely gone. Go figure. I always thought biggers tires would make it worse.
04 Sahara, with a lift, some stuff, and a few things, on some 33's, blah, blah, blah.
A perpetual work in progress. Too much to list, not nearly enough to matter.
My RigRater Score: 387RRv1.0 with a BOA of 18.92 (and just how exactly is this going to help me over that big arse rock?)
Always do sober what you said you'd do drunk. That will teach you to keep your mouth shut.
~ Ernest Hemingway