Just check out TORparse. Tam (KeyboardNinja) is a Shadow tank that I know doesn't stack accuracy at all and yet manages only to miss ~3% of the time with Double Strike and 13% with Saber Strike. If the 10% were actually required, he would be missing roughly 9% of the time, rather than 3% (1% Legacy accuracy and whatnot).
Noxxic is just full of bad. It's almost completely out of date, uses flawed stat prioritization that ignores the realities of gearing in TOR (not to mention *vastly* overvaluing accuracy for *every class*), and generally just has *bad* information; as I've said to other people, if a bad that thinks he's good is doing something wrong, chances are he's read noxxic and has no clue how bad he actually is. MMO-Champions is *painfully* out of date, as are most of the other sites other than this one, mainly because a lot of people stopped posting on them when they quit the game 6-8 months ago. It used to be on the forefront of theorycrafting, but it's now a fair deal behind the times.
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).
It wasn't until the combat log was released and that parsers started actually seeing use that people started actually figuring out how much defense chance operations bosses actually had. The 10% you see recommended was simply a lot of players following suit when a developer said "tanks can experience returns from accuracy of up to 10%" when asked why there was so much accuracy on tank gear; it didn't mean that it was even *remotely* optimal, nor did it mean that you actually *need* anything approaching that much, but a lot of people jumped on the bandwagon, even if it didn't hold true according to *any* testing or analysis. It's this that most of the third party sites get their arbitrary 110% from, even if it's not true. It's also why I don't trust *any* of those sites or even expect them to be 3rd party verified: they're almost all painfully out of date and, even then, they were using arbitrary allotments rather than math to actually arrive at their conclusions.
You do realize you can't replace power with accuracy right? DPS trading heavily DRed surge for some accuracy (Your options are alacrity, surge or accuracy) is the best option for min/maxing but it won't make a huge difference either way.