PI isn't a great elite to rely on for a kill. Also, since they stack empathy on you, they end up wasting energy trying to kill you when you have a weapon on. Their build needs energy to function and isn't built to last this long. They were targeting you because you were doing so much damage, but they needed to lay down curses and hex in a timed pressure and follow up with a spike from Warrior with PI on Monk. They were playing their build wrong by targeting you, but it's an ask to conserve energy for a spike when they are under that much pressure.