How does Guard work? It's the ability to evade damage, so does that mean it's present in every attack? Does it only work until it's reduced to zero and then become ineffective for the rest of the fight? Does an opponent with 3 GD and A1 need to take 5 damage to break through this protection?
Yes - it behaves like 'quickly refreshing hit points'. When you take damage, it is subtracted first from your Guard, and then from your VIG score. When you rest for a minute, Guard refreshes. In your example, I believe Armor 1 soaks the first point of damage, then guard is reduced by 3 to 0, and then 1 point of VIG damage is applied.