I may be wrong in this, but Torment of Scarabs causes life loss, not damage. So I don't think it can be redirected to Jace/PW's (could be off on this, not sure on the ruling, but about 95% sure.) The Rack does damage, so it can be redirected to Jace/PW.
Punisher mechanics seem to be bad if you look at history. You have to make both halves of the punishing card work to your advantage at all times, and that's hard to do (this coming from someone that tried DESPERATELY to make
Blood Clock/
Umbilicus into a real deck long ago.) The only way I can think of is to have multiple instances happening for your opponent with only half, or none, of the instances happening for yourself (think Stasis/Vedalken Mastermind.)