Well, so I'll get straight to the point: It seems like Protect is probably bugged again.
Yet despite the tests that I've done, even among others, it seems simply wildly inconsistent with it's effects, so I can't quite figure out what the issue was. I had three different instances where the effect has been seen to be different. In the third case, I may have missed a descriptor, but nontheless:
In the first 'test', I really only had myself to work with. I grabbed the fire mercenary guy, Reynes, I believe, is his name, and went to the Arena, pitting up against the Winged Guardian. I simply stood next to him, and in every instance, despite having a shield and being adjacent to Reynes, I did not get any Protect procs, versus both the Guardian's Basic Attacks, nor Raven. They always hit him.
The second, two people helped me out for; I simply stood next to one person with protect active; this is a PVP situation, so I'm not sure if this had an impact or it was another inconsistency, but regular basic attacks were protected from. However, skills that applied basic attacks, specifically Sidecut, were not protected from.
The third instance is less of a test, and more of a consistency thing: Jammer Gammas, when they have protect, appear to be able to defend against autohits, such as Rising Tide.
Regardless of which is a bug or not, Protect is wildly inconsistent over a number of situations. (I was told someone had seen it work with sidecut before, as well.)
I can try to post debug pictures if necessary while trying to replicate all of the scenarios.