I made the mistake of thinking crash fired when you parried. My line of thinking was that with Ward of Blades it would fire alot more.

I believe it makes the check to fire when they parry you and then of course its your str vs. their str to determine whether or not it actually will fire.

Being a human hand/axe spec didn't put me in a lot of situations to make it fire when I really needed it. I couldn't drop str enough on most people enough to make it reliable. It seems to me like you need to really have a couple point str. advantage to make it worth while.