Your design/simulation is not realistic. Normally, the feedback is taken from a current sensor in series with the motor. Where is that in your simulation? In other words, closing the feedback loop the way you did it is totally non-physical.
The goal of a PID design should be to create a system which exhibits the best possible response (step response, slew rate, overshoot, ringing) BASED on the dynamics of the mechanics being controlled. You cannot just design an open loop transfer and expect that a mechanical system will follow. Instead you have to start with the mechanical system, figure out how it behaves instrinsically, and then design a feedback network which will (hopefully) get the best possible response from the mechanics...