Bard, Dragoon, Ninja, and then maybe Summoner and Machinist seem the most desired DPS. Red Mage joins the list in high-movement fights where instant rezes will be useful, especially if in a physical-dominant comp.

In my opinion, Samurai and Dragoon are among the hardest, but in a dummy fight, most of that complexity boils down to rote memorization. Ninja runs an interesting line between feeling smooth (aside from Duality's CD with the new 3rd-tier Shadow Fang) while still having a fair bit of nuance, and Bard isn't quite as simple as it looks.