Yeah, upgrade those weapons as much as possible. Don't bother with Sazh imo. If I recall correctly, I used Fang, Lightning, and hmmm was it hope? Yeah. You could always Aegisol buff before the battle and go straight to using a librascope item. If you're having a hard time, try L- Rav, F-Com, and hope as a constant medic. OH I almost forgot. Enter the battle with F- Sab, H- Med, and L- Med. Slow and slowga work on him. Then switch to the Para I mentionned first. Set up your paras so that You can switch between relentless assault and the one with sen, med, med. Switch back when you get scared. When he does destrudo, go to relentless assault immediately whatever shape your guys are in. Once he writhes in a tad of pain, go to your sab, med, med combo. Also have a paradigm for sab, syn, and sab. So you can buff up with shell again as necessary
I'm assuming your crystarium is full or very close for each of these characters. If that's not the case, do that first.