This is the first encounter with him, right?
I remember reading in a thread that Tiffany was having some of the same problems. If you want to take a look-through at how she finally beat it, here's the thread:
http://thefinalfantasy.net/forums/fi...ut-medics.html
I heard how hard he was, so I made sure that my party was ready for him. I had all my characters' Crystarium levels maxed out and all the nodes activated. When the battle began, I buffed up my characters with every stat-boosting thing that my synergist would do. I had my main cast a Librascope so that my AI characters would know his weaknesses, and made sure that I dealt with the Pauldrons and Ailettes first (the things to the left and right side of him). Then after that, I focused on staggering Bart as fast as I could, and healed whenever possible. I did eventually beat him by switching between a full-on attack paradigm and a healing paradigm. It's best to keep everyone healed when you get the notification that he's about to do his destrudo attack.
Hope that was some help for you.
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