I just defeated Zodiark. I have to say he was the hardest boss of all on this challenge so far. The fight took me 4 tries.

Because guns are no good against this boss, I had to rely on Gil Toss for much of the battle as that would do the most damage. Whenever his physical immunity shield went up, I would have to rely on Balance Motes. I spent hours farming for them until I got 99.

Anyway, on the 1st try, I had to stop since I had something to do. The next two times, I had a Game Over. First time was because I ran completely out of Phoenix Downs. The second time was because, two times in a row, my guys couldn't get the Phoenix Downs out in time to the other fallen allies before being killed themselves. Arise was too slow.

I had used so many Phoenix Downs that other time mid-battle because I got caught in a vicious cycle where all Zodiark was doing was using Darkja a lot and after each Darkja, just beating the crap out of my guys and because he had gotten so fast (upon using Limit Break), he was 1-2 hit killing them a lot.
I had found that the best thing to do when getting into this bind was to use Quickening Chains as I had a lot of Ethers on hand. With Quickening Chains, I'm guaranteed to get hits in w/o getting knocked out by him constantly and having constant Phoenix Down cycles. I had noticed that when his HP gets below a certain %, then he does the Shift and then Paling.
When he put the Paling up, I had set everyone to use Balance Motes (if self HP is below 70%).


The way I managed to beat him this time was the following:

I had Balthier, Ashe, and Penelo in the party. Ashe and Penelo had the most MP, so that's why I used them.

I started out having everyone use Gil Toss at the beginning. Everyone entered the battle with Protect(ga), Shell(ga), and Haste(ga). I didn't bother using gambits to get rid of the Blind caused by Darkja because Blind isn't going to affect your ability to use Gil Toss, Quickening Chains, and Balance Motes. So I turned all status removal gambits off so I could spend more time dealing damage. I did have a Vaccine gambit because his attacks can randomly inflict Disease. I manually gave remedies to anyone affected by his Lvl# status attacks.

In dealing with Piercing Graviga, I temporarily took Bubble Belts off of everyone so they wouldn't take as much damage from the attack.

After he did "Limit Break" and I got into the cycle where he was using Darkja a lot and hitting my guys really hard, I starting doing Quickening Chains quite a bit. I had everyone set to use Ethers at Self:MP<10% so they get their mist bars filled quickly and then I could start another chain.
Also, after he did "Limit Break", I turned some of my buffing gambits off so I could focus more on dealing damage.

Once he readied "Shift", I had someone use a Dark Matter. It dealt 42000 HP of damage.

After I used the Dark Matter, he was almost dead. After one of my guys used his Ether to get his mist bars filled, I started another Quickening Chain as he was readying Battle Cry (meaning he's about to put up the Paling), and I managed to defeat him with that.

I only used 3 Phoenix Downs and 26 X-Potions this time. I didn't have to use any Balance Motes.