Shatterpoint just needs a rework in my opinion to fix him, because you are right he's pretty useless right now. The problem with Shatterpoint right now is it barely ever procs and it almost never procs on the enemy you want to attack.
I think it'd work great if Mace had a chance (adjust % based on balance) to expose any enemy he attacked, and if he exposed them, he'd immediately get a bonus attack. So you get in one whack, it procs, then he hits them again in their exposed state.