DPS class with the fewest buttons?

[Humorless]

Bard and Black Mage are the only candidates. Bard rotation is even easier than Black Mage.


Edit: as for the other classes:

SMN - brings pet skills with it and a bunch of odd oGCDs that come in "sets" (aetherflow consumers, pet buffs and general buffs)
MCH - my hotbars are all full and I have my turret placements on my mouse and AOEs on somewhere I need to click. By far the most ridiculous of all dps.
MNK/DRG - the rotations are simple enough but the need to move constantly narrows down what you have access to on keyboard
NIN - slightly easier than the other two melee but the mudras waste space on the hotbars


As for the geniuses saying MNK has no oGCDs:
IR, B4B, Invig, Mercy, Mantra, Shoulder Tackle, Elixer Field, Steel Peak, Howling Fist, Perfect Balance, Purification, Tornado Kick, Meditation/Forbidden Chakra (13)
DRG:
IR, B4B, Invig, Mercy, Mantra, Jump, Spineshatter, Dragonfire, PSurge, LSurge, Battle Litany, BotD, Leg Sweep, Elusive Jump (14)

They're pretty much the same. If you want to argue that Tornado Kick (for example) isn't used much we can do the same for Elusive Jump and DRG Mantra. Neither of them are easy on buttons considering you're still WASDing the hell out of your keyboard at the same time.