Solver is too performance heavy

[chenji]

I'm rotating player by default using AddTorque, I do not know why Chenji mentioned it

If you did then you can just ignore this checkpoint. How and where you rotate actually is important. Do you rotate in FixedUpdate? If not try to do that. If you rotate in a late stage, you'll probably also get 1-frame-gap issue. 

Also did you try my suggestion to manually change particle position in solver.OnInterpolate to keep rope follow player's hands? I think this should work as a last resort.