There's a word for that
I can see why you needed Power Break, that miss on Ifrit after Darkness wore off was very lucky... Still, maybe you could just run with it and pretend it worked properly anyway The fight really looks to involve a lot of luck as-is, and trying to get Tidus hit would cut the odds of success by another 2/3, which really doesn't sound worth it... I don't think anybody will deny that this fight is good, it's just a matter of how extra-good you want to make it.