YouTube - Lunia ç*”ç©¶æ‰€BOSS
Eh? Siegs are useless? I think not. If you have one healer, you can apparently solo it. If he didn't go suicidal at times (ie. with the transformation pot, tanking the boss at the beginning) I'd say he could solo it. And the same goes for Tia. It's called knowing the boss's moves. And knowing how to dodge.
And yes, there's a Magic Defense near the beginning that apparently renders the spinning things pointless while he broke the controls.