Another thought here. Rear tires don't just wear from extra weight ( down force). But pulling the extra weight of the pull force. Even though you equalize the weight with the hitch you are still pulling the same weight. Therefore your tires need to work harder.
I like the tire slipping idea.
If your bars are to stiff there is no flex or give
Then your shocks are rendered useless or can't adsorb properly thus on a bump your tire could skip without notice. Even a 1/2 inch or so of slip will Start to wear.
Rotate tires and change your bars.
May you have at least one sunny day, and a soft chair to sit in..
2008 5.7 L V8 Sequoia
AIR # 31243
WBCCI # 6987
FOUR CORNERS UNIT