Nifleheim7 was right, this is definitaly the best strategy (especially for dark aeons)

Break Damage Limit
Evade and Counter
First Strike
Triple Overdrive

Break HP Limit
Auto-Haste
Auto-Phoenix
Ribbon

With the weapon all you really need is Break Damage Limit (60 Dark Matter) and you MUST have ribbon. I managed to kill Dark Valefore, Dark Ifrit, Dark Ixion and Dark Shiva without a ribbon but the rest of the Dark Aeons are impossible without at least 2 members equipped with this. As long as one member of your party has first strike (or dark yojimbo will anihalate you before you get a turn), you can customize the rest to your taste.