Tuning of servo-drive

Hi,

I've been trying to get a couple of chineese CTB servos with drives to get to work via EtherCAT. I'm not quite happy with how their follow-error is at the moment. But i'm wondering how i could resolve this, because most "how to do a PID tuning in LinuxCNC"-guides reference closed loop circuits via LinuxCNC. But since these drives are connected via EtherCAT i thought that you guys might also have had to do the same with your drives. 

Currently my "step response" looks like this:
 
...it seems to be conservatively tuned from the factory, since the follow-error is quite large...and i'm a bit puzzled by the flat bit, it seems like it slows down before finally trying to hit the target...

So my questions are essentially:
1. If you are using closed-loop servodrives without an autotune function(or with an undocumented autotune function, as with my drives!), how did you go about and tune it? 
2. What are a "good" stepresponse for an axis? And what should i aim for with regards to follow-error to get "good enough" results? I know it is a "what is the diameter of an elastic band"-kinda question, but i find it hard to figure out what to aim for, so any input or thoughts are appreciated....

/Thomas