She wouldn't have been much better with the reworked scepter, probably worse. It was one pulse every 4 seconds reducing their MR by 15% stacking 3x. The enemy needs to have at least 133 MR for one pulse to equal/greater than live scepter MR reduction, and Kat is not hanging around next to an enemy for 12 seconds to get their MR 45% lower. I'm not sure what the aura range was on the rework but it was obviously less than live considering it also did damage...I think it was similar to Sunfire's aura.
The rework was intended to push the item towards AP bruisers/tanks (e.g amumu, sej) who get in the middle of a fight and stay there. It was not intended for AP assassins. Hence the dramatically reduced AP (30 vs 70 on live) and the addition of health to the item.