Insane Difficulty: Trouble at the _____ - Insane Difficulty

I don't really know what anybody else did, but I equipped Cecil/Kain with all the metal gear they could ever want and dumped them in the front to take hits. Everybody else was in the back spamming Bahamut and Ninja Stars or something.

I don't really remember my setup or levels too closely, which means that the dungeon didn't stand out to me as being especially difficult. If you haven't tried just giving it a go I suspect that you'll probably be okay without doing anything too drastic.

Really? How did you manage to get Bahamut so early?? I probably missed a lot of things...

There is some gear sold that ignores the metallic effect. There's an NPC in the castle and perhaps the town that give you hints about it.