Not really.
After having 2 Lexus dealers tell me there was nothing wrong with it I brought it to a local, highly regarded 4x4 shop and they found that the drive shaft was almost dry and needed to be lubed. That seemed to help quite a bit.
I also just swapped out the crappy Iron Man dealer tires this week for Toyo A/T E III's and so far I love 'em and that seems to have further mitigated the issue although I'm still getting it intermittently. Not sure I'll ever identify the ultimate cause or eliminate it entirely.
Lexus did check the alignment with the old tires and said it was out a really small amount and recommended an alignment after I get the new tires so that's next which I was planning on anyway. Can any shop do the alignment competently?