The turret portion of this flashpoint is a bit confusing, but can be completed easily with the following strategy:
Have your healer stand on the container in the middle of the turret positions, then have the rest of the group operate 3 turrets. At this point you want to turn your turret 180 degrees so you are facing towards your healer and the other group members on their turrets.
This allows you to fire across the other turret positions and quickly kill any mobs that get past the turret positions and go after the healer. Doing it this way made it much easier for our group. It just took a little creative thinking to get past
Best of luck!