The information I use is based on the information my parser tells me (I use MoX). When I have no accuracy and never miss with my F/T attacks *at all* and miss only ~3-5% of the time with Double Strike and Spinning Strike, I feel pretty confident in saying that, no, raid bosses do *not* have 10% Defense chance, and, in fact, accuracy is less valuable than Power, which contributes more to your DPS based on Math (when I can prove that, as a tank, stacking Accuracy provides less DPS than Power when you're only using your basic attack, it's pretty well been debunked, and I've done it a few times).
The operations training dummy is supposed to have the same defensive stats as raid bosses.
is the result of accidentally replacing the wrong enhancement yesterday and dropping my accuracy to 98.43%, rail shot hitting only 97.96% of the time - aka the expected amount if it has 10% defense considering that railshot has 10% bonus accuracy. It could be slightly
lower and that result was just me being slightly unlucky, but it has
to be higher than 8.43% since I'd have been hitting 100% of the time otherwise. The rapid shots results would even indicate that the defense is a little bit higher (86.48% accuracy in this parse), but that's probably just bad luck.