Good post, I may have missed it but one thing to consider.

A warrior with unchained and infuriate up is technically higher dps than with defiance off due to the crit b us on wrath. So depending on the timing of tank swaps you can stay in defiance and maintain pretty high dps as well and then be ready for the swap with defiance still up. For any sustained dps situation though, then you would want defiance off for max dps.