I just did it with that same group ( emp version of SJ+ 3sorcs ) at lvl 19. The whole instance was a joke up to the last boss. I did exactly what remanz said.. i kept my tanks back to the console behind the boss..so i could see the AE placement and move my slaves accordingly. The first few times i wiped due to not moving out of the ae fast enough and wasting too much time on adds. 3rd attempt i killed him by focusing on the boss better AND moving my slaves ASAP when i see the ground target. ( also using the knockback helps a lot to keep adds away and i have a click button to place shields on all the slaves instantly.