Please consider greatly increasing the base accuracy of Violent Flourish. Magic Acc and other enhancing equipment could affect the duration of the stun, but the effect should land with far greater accuracy and reliability.

tl;dr

At release it was apparent that specific Notorious Monsters were selected and granted immunity (or some extreme level of resistance) to Dancer's stun. Please keep in mind that these said NM's were susceptible to the spell Stun.

In time, gear was released which enhanced the accuracy of the ability however certain tier NM's still pose absolute immunity (or far greater resistance requiring some level of enhancing equipment).

DNC could benefit from an "A+" ability as most of what it has is versatile and quite impressive, but arguably not focused enough as a job to have a spot reserved in some group-based endgame content.