DNC esprit gauge is bugged or tooltip reads incorrectly.

The esprit buff reads as follows "The Esprit Gauge is increasing when you or the party member designated as your Dance partner successfully lands a weapon skill or a spell."

I'm either misunderstanding how esprit generation works, or the tooltip is incorrect or bugged. This makes it sound like you should be generating Esprit after EVERY single weaponskill or spell cast by you or your dance partner. However, it's pretty evident while doing solo content that you're not generating Esprit every single weaponskill you cast but rather you have a CHANCE to generate esprit.

Bugged or intended?

it says accumulate meaning that it has a chance to gain esprit

I think it's a tooltip error they need to fix so that they're not misleading.

Esprit is RNG. The tooltip in the other languages makes it more clear that there is a chance of Esprit gain, and that it's not guaranteed.