Another thing to note is that if your defense is lowered by an opponent then the following will happen.
If the targeted defensive stat is +, it goes down to ~ and if ~ it goes down to -. If it's already minus, there's a different story going on. If it's already - and your defend succeeds, then that - becomes non-existant and it's like your defend never happened. Then you take all of the damage regardlessof whether or not you defended. The Defensive Stats, after becoming non-existant, become negative. Then you begin to take more damage. The stat can only be dropped 5 times but for each time dropped, you take 5 more damage and this applies to just taking damage in general, not just when defending. That means you can take up to 25 extra damage if your opponent pays close enough attention to offing that defense so stay sharp.