Let the music play!
I was looking at the Tiamat fight lately and wondering if there weren't better approaches to fighting him. Reflecting Dark is fine, which is what Youkai does, but that takes a while, especially as Tiamat takes half damage from Dark, and the casters have to pause occasionally to Charge. Chaining Quickenings would take a while too, but get a good amount of damage in - perhaps useful for taking the last 1/4 to 1/3 of his HP off if you chain up to Cataclysm. Perhaps resorting to using physical attacks might be faster, but obviously more risky. I was planning on buying a Main Gauche anyway given it's decent damage and huge evasion boost, so that's one character sorted physically (probably just for Vaan/Basch though). Perhaps the true solution is a combination of these approaches, but it would require a lot of testing I'd imagine.