How do I get rid of duplication

Agreed.

No function (or pointers) required with my array of servo objects:

pwm[i / 16].setPWM(i % 16, 0, turnArray[i].currentPos + turnArray[i].offset);                                                           

or, more efficiently:

pwm[i >> 4].setPWM(i & 15, 0, turnArray[i].currentPos + turnArray[i].offset);