I wish battles wouldn't punish us for doing too much damage
I think the title says it all but gear and echo, things that are supposed to ease content over time actually often make it harder. Phases get pushed and unpredictable things start to happen. Sure if you know that a boss goes to such and such a phase at such and such a percent of hp you can hold back but that seems really dumb. A hero of Eorzea has to pull their punches? C'mon.
One solution is to have more fights based on x-amount of time passing or such and such an event happening (killing an add for example).
While on the subject I think that item level sync is silly too. But I guess I'm used to single-player RPGs where if you're having trouble you can get better gear or if you get really good gear you can go back and really wreck enemies that might've once been difficult. It's a great measure of how much a hero has grown over time.
And on THAT subject, FFXIV doesn't do enough to make us feel like heroes. The quests should be epic and the npcs should throw us a feast or parade and the citizens of Eorzea should cheer us. Of course this can be overdone but you get the idea.