While I can't comment on Turn 5, there are quite a few instances where the PS3 doesn't load enemy animations in sync with their cast times. For instance, against the Miser's Mistress, sometimes she'll begin the casting animation for Bad Breath then immediately cast it. Luckily, with her, she has red AoE markers--unlike Twintania's divebomb which doesn't have them--and they always appear in sync with her cast time, whether or not she displays the animation.

I guess a more appropriate example would be Isgebind in Stone Vigil. I'm assuming that divebomb works similar to Isgebind's breath attack, and I've only occasionally seen that go out-of-sync. It really depends on how much stuff is happening on the screen, whether or not their animation will be delayed in comparison to the actual attack.