So is there an actual reason that you chose a topic as emotionally frought (and thus mind-killing) as rape, and at the same time created a made-up scenario where we're asked to ignore anything we know about "rape" by being forced to not use our judgment but Omega's on what constitutes utility?

And anyway, i think people misunderstand the purpose of utility. Daniel acts according to his own utility function. That function isn't obliged to have a positive factor on the rapists' utility; it may very well be negative. If said factor is negative, then the more utility the rapists get out of their rape, the less he's inclined to let them commit it.