That I know and not what I asked. What im curious about is what the rate gain is from your partner. Does it only come when under the 20 second dance?
The monk and Sam in my group are debating. Obviously the monk with a lower gcd would be the preferred partner, but if they only gain esprit under that 20 second buff then I feel like giving that single member 5% buff to a SAM about to triple midare and hissatsu would be a bigger gain than 2 extra Rick's of esprit for the dancer
Apologies! Your question came off more asking what it is to me.
Esprit isn't 100% chance and seems designed so that it can work with the spellcasting classes, so I think there is still testing going on as to whether there is an internal GCD or not limiting how fast you can gain it.
In your group composition I'd go with the SAM for single target fights (your reasoning is sound I believe) but for AOE I'd go with the Monk due to the faster monk attacks + you wanting to AOE more.
Either way, I'd do a lot of your own tests for this because mine have come back as fairly inconclusive so far.