tires overloaded?

I'm a fan of big safety margin on tires. I live in the Southwest, frequently drive across smoking hot roadways for hours, often with 18' cargo trailer in tow. I was running a few different brands with the highest capacity E rated tires I could find. I was always 'just' at their max with a full loaded camper and trailer tongue weight in total. Then on one trip I could feel a growing vibration. At a fueling stop I was shaking wheels, wiggling front suspension components etc trying figure out where it was coming from. Then I saw it.. the tread on one rear tire was getting scarfed bad and the shape of the tire was changing, the tread was not longer totally flat, but had kinda a radius to the tread. I got on the phone and Googled tire shop that was close, and when they pulled it there were multiple blisters inside the delaminating tire. After that trip I got some 19.5 Vision 181 rims and Double Coin RLB 490 and have at least 75 thousand worry free miles and they ain't done yet, I plan to go to 100k and regardless of condition I will discard haha. I rotate about every 5k miles to keep them nice and flat, run 8oz of beads in each for balance and the only thing I fear is throwing my back out every time I rotate them!