@Midnight: No, what it is is that in RTW the sheild was unaffectd by AP. The diagrams and in files notes say this is still the case, when in fact CA have changed it.

Before a unit with 6 armour and a 6 sheild got 9 defence vs AP attacks (because the AP halved the armour to 3 points of effective defence).

No the sheild is also being halved so the sheild only provides half it's value against AP attack as apposed to the full value. That is a pretty big change overall and is tottaly undocumented as far as i know.