So the ropecaster pins the robots in place? I think I don't understand how combat works in Horizon - I've been doing it all wrong.
The ropecaster acts a lot like the elemental weapons, you can see a bar on robots when you stick ropes to them. When the bar is full (enough ropes attached) the robot will fall down and you can do critical hits or overrides on them or just do more damage. Enough damage and they get free earlier. I mostly use them on fast and big robots.