$toss is cheap, dont lower your self to their level

invest in four pairs of winged shoes (50,000 gil each from mirage town) They give auto-haste2 and instant initiative in battle. because you all have instant initiative, use your first turn casting your protective magic.
now, you can keep up with x-deaths speed so should always be able to heal straight after receiving an attack. Also, if a character dies and is revived, they will still have their haste2 active without having to re-cast it.

It helps to have a blue mage in this battle or someone who can cast blue magic. you can cast reflect on your party and rely on whitewind to heal. Cast big gaurd/gaurdian (before casting reflect of course) and also i read in a guide somewhere although havnt tested this, you can cast condemn on the very back segment of neo x-death.

Regan, shell, protect, blink, and haste are your friends :P