I've been testing this out, and there is a way to get a 4k+ crit everytime after finishing blow. You basically have to swtich to a bow after you knockback, use finishing blow, then switch back to a sword and decap.

Its very usefull at 1shotting all non tank classes, and even on tank classes you can take 50% of their health in 1 shot

I've been waiting until they are getting up off the floor to finishing blow, so it misses, and then Decapping.

But this way sounds even better, if its a definate 100% method, and you can do it while they're still down.

haha.. uber:D! guess it wouldnt last longer..