This is a tad delayed but 320/120 means nothing for SCH, as far as nuking goes. If you're just going BLM mode, use Alacrity/Klimaform. Assuming you have Dark Skill capped/gear (Also assuming it's based on Dark skill), Klimaform gives something like 50 MACC? I have no testing to confirm or deny but that's what I've read on a few different sources.
Klimaform lasts 1 minute, recast is 3 minutes. Recast with Alacrity is 1 minute, 30 seconds, and recast with Alacrity and Relic feet is 1 minute, 12 seconds. It's virtually never down. And when it is, that gives you a good chance to recast buffs/weather.
Edit: This is what I nuked in at Kirin on SCH.
Obviously, swap out the Aquilo's for Auster's, the elemental earring for Novio Earring, Cobra Crackows with Yigit, and use Wind nukes and Anemohelix. Resist rate wasn't floored, but it was close.