There have been no "stealth fixes". We haven't changed anything relating to armour recently. This thread prompted an investigation, and it does turn out a few of the most recently added armour modifiers (not all of which are in the game yet) were applying to generic armour, but not to armour against projectiles (which is a different stat calculation to account for Titucius' Span). The most significant source of armour that was affected by this is the Grand Spectrum unique jewel. This will be fixed for a future patch.

No. As I already said in my first post, this applies only to a few recently-added stats, which were added to one calculation, but not the other. Most of these stats aren't in the game yet. All will be fixed in a future patch - I'm currently working on this fix and improving the system to reduce the chance this happens again.