I'm having some trouble understanding what/how I need to input parameter values into the code to produce a desired result. For the 'expect single strings' example, I assume the lettered values represent microseconds and then degrees per each defined servo.
You should be testing the code to see the results. Using the posted code, sending the first line below from the serial monitor to the arduino will position myservoc at 30 deg., myservob at 180 deg., myservoa at 70 deg., and myservod at 120 deg. The second line will send 700us to myservoa, 1500us to myservoc, and 2000us to myservod.
30c,180b,70a,120d,
700a,1500c,2000d,