If that were true I would never miss with my Master Strike, Dispatch, Throw, Leap or Overhead Slash. I have seen all of those miss on multiple occasions.
You've got 4% accuracy from external sources (Legacy and spec). You had a ~14% miss chance with your basic attack and a 4% miss chance with your special attacks. Ergo, the boss has an 8% defense chance (104% accuracy reduced to 96% accuracy and 94% accuracy reduced to 86% accuracy), which is within the realm of what I've generally heard. Your parse is completely in line with what I was saying. Honestly, I find it likely that different bosses have different defense amounts, which is one of the reasons why it hasn't really been pinned down.