I think it works as it should, just the description is woefully inadequate.
Why would you waste 2 AP on casting a spell that might or might not hit depending whether someone walks into it's AOE ?? Why don't you just go and cast Ricochet or something else and get the instant damage for the same AP ... This is what I thought would happen according to the spell description and why it took me so long to use this spell.
It makes total sense to do initial damage and give you a non-guaranteed chance for additional damage. The fact that it is AOE makes it possibly the best skill in the Huntsman arsenal.
One could combo in a party chicken, rupture tendons and reactive for some nice damage.
