A character doing literally nothing during an expected swing of a sword is going to look so weird that I'd sure hope that it's obviously a bug.
You can check out a build guide video for that skill and see that every attack has animations. Some of them are shared because casting a fireball and casting a volcanic orb are similar enough that the mage doesn't need to make two different gestures.
Edit: triggered abilities don't have character animations because you need to be able to do stuff at the same time.
Edit 2: wait, do you mean VFX?