HonorableJay, nice run. Unlucky with that bell. Does the batarang have to hit in a specific place or does the centre of the batarang have to pass through the rope? Do you find that particular spot a little easier with the movement keys on the PC? I'll give it a try when I get the chance.
It seems like the actually hitbox to cut the rope starts just a bit under where it connects to the scaffold above the bell, which explains why it took me so many tries to actually cut it. As for the controls, that spot is a lot easier for PC controls but still not necessarily easy.