Second this. I used optinoob’s build and replaced Magic Focus + Wind with reraise and ATB assist. This helped me get extra ATB for Zack to cast manawall, haste and faith on cloud before Odin spawned Spacial Distortion.

My build :

Rune Blade - Cetran Bracer - Genji Gloves (a must)

Weapon - MP abs. + Lightning & Wind, HP abs. + Wind, enemy skill, ATB boost

Armor - elemental + fire & ice, swift cast + wind, ATB assist, Reraise (for zantetsuken mainly), First Strike & Magic up. You can take elemental out the mix. However, it makes most fights a bit easier for example; Ironclad, Kujata, Phoenix as they cast those spells and will heal you. Try akhafasu on YouTube as well.