Some enemies it seems like it doesn't trigger for me on. Coblyns for instance, I lu... oh one of them was a level lower than me, maybe that's what it was.

Started a chain on a Bomb. But after Chain #1, the next enemy linked with two other Bombs and it was time to flee. The enemy missing a lot may have played a role in my survival in combination with Foresight for the parry + Second Wind for the heal as a R30 Gladiator (at the time).