Another thing about Sephy I forgot to mention... to avoid his Meteor Storm, just Dodge Roll and pray. Also, all of his sword attacks can be Guarded, not just Omnislash.
ALSO, his early pattern is Slashx3, Flame Pillar, repeat. If you hit him with a 3 hit combo, then roll away, he'll use flame pillar, leaving him vulnerable afterward to repeat the process.
Not too hard...