Actually I don't understand why armor even acts as a 2nd healt bar. When I first saw Larian talking about physical/magical armor I assumed it'd be like this: normal attacks and skills damage healthbar. Armor only acts to block cc and can only be damaged by special skill effects specifically targeting armor.
This way it'd greatly reduce cc reliance and force players to choose between killing an enemy quickly and breaking armor to cc instead of simply breakung armor with alpha strike and then stunlocking to death.