It looks like it's not that strict though. You can basically fill any of the extra FoF GCDs with anything--including Fast Blade or Riot Blade--as long as you FoF promptly every 60s and you don't break your 1-2-3 such that it costs you a Divine Might. They made it really hard to do crap damage. And even when you can cram two Mighty Holy Spirits and a Royal Authority into a single FoF, the funny "just do a bunch of weak Holy Spirits" rotation still sometimes pulls ahead.