Make sure if you have Marauders in your group that they dont use force leap during that part. Me and the other Marauder in my group basically cut that out because we notice sometimes then a cleave and an overload go off at the same time you can only see both casting if your bar is set to max size.
If you run with Two Marauders assign one to cleave an done to overload they will always have their interrupt up, try not to use force leap. If your using any other class with a longer cool down on their interrupt set up a three person rotation and call it in vent.
Once we stopped force leaping we got rid of the double cast and it makes for a nice clean run.
Interesting Strat. I know that were gonna try that. The Phantom overload happened a few times. I've noticed it happening whenever the droid has just been despond and is moving towards us. So me as a sentinel I cannot interrupted because it's not anywhere near us anyways. But at the same time there is no Castebar.