I love the rotation (as boring as people think it is) of Dragoon. On top of that, I love how the rotation rewards you with an upgrade of your combo starter if you hit a couple of your positionals. It's a nice visual output that says "Good job!" for hitting positionals, while most other classes get slightly bigger numbers and you have to think "Did I hit that positional, or did the boss turn before I could get it off?"; That visual indicator makes me happy.
Red Mage is my favorite "I want to play, but I want to relax too" DPS. Its rotation is simple but offers some optimization that you can do to stand out. It's a very meditative experience.