It'll be interesting....

Garuda will be weak to Ice
But there are no Ice combos and the actual Ice spells are more for status affect than damage....
Garuda will be strong against Fire
So it looks like Thunder>Thundara>Burst is the way to go for a Mage
Fists of Earth for a Monk (because Fist of Wind/Fire would be ineffective) meaning monk probably wont get much use
If you get knocked out of healing range A LOT then a PLD tank might be the way to go for self heals... although it would have to be seriously needed to warrant choosing PLD over WAR
Garuda seems like it would have some serious ranged AOE attacks (Like Ifrit), so BRD isn't quite as safe a DD as it has been on other fights
Dragoons jumps could prove useful in a fight like this

All just fun speculation of course... I could be 100% wrong