EMDR can be very effective even on complex PTSD but because of the amount of abuse or trauma it is not a quick process. With EMDR you work on one trauma at a time preferably the oldest one first because everything else relates back to that.

I have been working with my therapist for close to a year and a half now I had all kinds of abuse physical, sexual, emotional, and neglect from the ages of 2-20. So the problem is there is so much crap to work through no matter what modality you use it's going to take a very long time. But yes EMDR can widdle it down 1 trauma at a time. You do want to be sure you have somebody highly-trained in EMDR if you using it for complex PTSD. Personally I think the success rate with using EMDR comes down to the therapist performing it they have to have all the tools and tricks to help get you through it.