BLMs can get away with about 12-13 keybinds if they really want to, even at level 60. Granted, that means leaving out the stuff that'll really optimize your DPS (Manaward/Manawall, Aetherial Manipulation, etc), but you'll be a fully rotationally functional BLM. It's probably the job with the lowest skill floor, but has heaps of room for little things to optimize if one chooses to do so.