Then you are experiencing something we have not yet. Its quite possible to target the pylon while a ball is spawning inside (sorry if I confused you), and its also accurate. On only one occasion the ball wasn't targetting who it was supposed to be, and that was because that target died as the ball was spawning.
I think you may be confused with something else. Or you are doing something wrong. Who knows with all the bugs.
I don't mind you trying to comment in and help people, but you're spreading misinformation. I understand you haven't been able to kill this boss yet so you probably haven't figured out the mechanics. Keep working at it, I'm sure you'll get it.
I also have videos up for Annihilation Droid XRR-3, Gharj, and the Infernal Council so you can work on those nightmare modes. I'm sure you'll get your first kill in on them soon. Grats on your nightmare pylon kill by the way.