Yes, AoE math is not perfect and may not trigger properly when enemies are not packed tightly enough or if you select an enemy at the edge of the pack. This issue is not related to any particular class, it affects all jobs.
We have plans to improve combat geometry algorithms, so in the future it should become better.
Thank you for your feedback.
Just so you know, i appreciate this, and do not mind if it was done before my own suggestion.