I decided to throw the Insanity Thresher on my Barb and give WW a shot on some Hell cows but was unable to get the Amp damage curse to proc. I had originaly equiped the Saracen's Chance amulet and had no luck with the proc. I then tried swapping out the thresher for duel IK legendary mallets for a total of 30% chance to cast Amp damage on striking but it still didn't proc. I was wailing away at a massive pack of cows which should have procced the curse. Any ideas?

On a side note, that pack of cows chewed through the durability of that thresher in about 6 passes. Looks like a Zod rune will be a must for WW.