i just be him yesterday, my levels were lower 50s. my party was rikku with alchemist, yuna and paine with dark knight. its good to have 99 potion/high potion.

have 2 dark knights and a alchemist. have the dark knights know all of the proof abilitys(curse, confuse, ect) the alchemist should know mega-potion stash. and have items that can cast protect, reflect, and shell.

before the battle go in with rikku equiped to the garment grid with double hp (dont go into the batttle with alchemist equiped. if you do then you wont have hpX2), and a confuse proof. have yuna and paine have the helios grid(the one with protcet on in), and accesories that have +attack and defense.

start of the battle with rikku equiped with anything but alchemist and change ASAP to alchemist(make sure to go thought the double hp thing). have yuna/paine equiped with anything accept dark knight, and change to dark knight ASAP(go thought the auto protect thing).

once every one has changed, have rikku mix potion/high potion to make mega potion. and make yuna use a item with reflect. and paine use darkness. then have rikku mix a item with protect and shell(not really a must do, but its good to have), and keep yuna and paine useing darkness. then use mix to a mega potion/darkness over and over and over.

after awhile he'll use bloody breath about 5 times(not in a row, thought out the battle) and yuna and paine will be hiting for trout. (this is the hard part) so you should kill off yuna/paine and revive them. use reflect on them and keep doing the samething as before.

after awhile he will die or run out of mp. if he runs out of mp he cant revive his buddys and you can go on a onslot of just attacking him.

good luck.

edit- wow, i think this is my longest post ever.