I re-watched the PLL and at one point Yoshi-P performed a Technical Finish without the esprit gauge active and it gave a separate red version of the Esprit buff with a 15s duration but didn't activate the gauge timer. The gauge timer is probably only intended to indicate the duration of the normal Esprit buff which is shared between you and your dance partner. Technical Finish gives a separate party-wide version that won't overwrite the timer on you and your dance partner.
The potency is probably low enough.
It takes 1.0s+2(1.0s)+1.5s=4.5s to execute a complete 1000 potency Standard dance.
We can't really just divide the potency by the recast times like we would with most cooldown abilities because unlike other cooldowns, dancing prevents all other actions (similar to jutsu). So while dancing, you're not getting the 103.7~166.0 potency per second from basic weaponskills.
Let's consider RDM for a moment, which is supposed to be on the lower end of the DPS scale. Let's also adjust the potencies of JoltII and a Verslowspell to a 2.25s GCD so we can fit both of them into a 4.5s window. Let's also adjust Fleche's potency for a 30s cooldown, and also take into account that RDM potencies are worth slightly more than DNC potencies because RDM gets +30% damage trait while DNC only gets +20% damage trait.
JoltII: 250 * 2.25s / 2.44s * 1.3 / 1.2 ≈ 249.7
Verslowspell: 310 * 2.25s / 2.44s * 1.3 / 1.2 ≈ 309.7
Fleche: 420 * 30s / 25s * 1.3 / 1.2 ≈ 546.0
So in one 4.5s period every 30s this hypothetical DNCified RDM could do about 250+310+546≈1105 potency. This is a little higher than the potency of Standard Step in 4.5s, and this is during the weak part of the RDM's rotation, so "too high" is probably something the Step potency is not.