hmm... so in the original ff4, the battle doesn't stop after cecil hits yang after his second kick? you actually have to drain all his hp? i haven't played through j2e's translation in years, so i don't remember.
i know that no animation doesn't mean it didn't work, thus this: "or is he casting it but there's no animation, so i don't know it's happening?"
i didn't really think about it before, but i started using some utility spells(as opposed to attack/healing spells), and it's really helping. safe seriously trimmed yang's damage down to nothing, and blink helped me build up the safe barrier.
also, i ended up hitting him with slow as an experiment. he used a different battle message, so i take it that i got the right spell to cause him to use the speedsong counter, but he still seems slowed down. maybe it's just me.
i finally got this to a manageable level. it took like 4 or 5 castings of safe and a half dozen uses of blink by tella to get me there, but he finally can barely hurt me. now i can just keep plinking his hp down slowly...