I didnt discover this someone else in a thread did but I wanted to let others know again because i keep seeing it brought up over and over. Be aware that I do believe it is still a bug when he gets stuck at 3 charges but it IS 100% avoidable.
When Soa goes into his shielded mode and you have to jump down the platforms make sure you only engage and fight ONE pylon at a time. Also dont skip the very first one on the way down. Usually right after he breaks the platform from under your feet or you drop down it takes about 2 seconds to become targettable. Just wait for it and take it out and move to the 2nd one.
AGAIN do NOT engage more than ONE pylon at any given time. Its not saving you time to have someone running ahead killing them anyways and if he does bug out it will cause you to have to exit area and run back which we all hate doing! (dang it Bioware make the speeder go up to Soa's room already!)
This worked EVERYTIME we tried it in normal AND HM so if any trolls come in and deny this works 100% of the time they are lying or they are bad and doing it wrong.