First and foremost let me say I love the duels. The idea of doing a difficult raid boss by yourself with difficult mechanics that require you to push yourself to beat it is pretty awesome. It gives me major Mage Tower duels from World of Warcraft which I loved.
My only gripe with it is the wait. I can't tell you how much Hunt for Red Choctober's I've done only for someone to beat me to the duel even though I'm hanging with 4 Notoriety.
Even then, the wait time for these FATEs are another wall to contend with. With no real way to know when or if it will spawn it can somehow be frustrating, especially if you're trying to learn the duel.
Which on top of that leads to others just afking at the main base waiting for these FATEs or Critical Engagements to spawn. You can go to any base and see at least 10-20 people just afking waiting.
I hope something like duels shows up for Endwalker, but I hope it's not behind a wall of waiting. Maybe have us do a number of FATEs before we can just talk to an NPC and attempt the duel. I just think waiting around and contending with others for something that takes multiple tries to learn and conquer is a real drag.