While i was preparing myself for the raid tonight, i was checkin if i had full enhancement gear and when i've equipped the 2h weapon my armor didn't change, and when i've equipped the shield + 1h mace(elemental spec) back it added the shield armor as +armor... and the result was:
I relogged but I had the same amount of armor after the relog too...
Short story:
1. elemental spec(dunno if it matters) with normal gear(1hand + shield)
2. equip 2hand weapon and the armor from previous gear(1hand + shield) will remain
3. equip 1hand + shield and u'll add more armor