If we're talking maximum optimization, mine would look like this I think:
SMN(shit just lines up so fucking weird) > BLM(got a lot easier with ShB tbh with triple cast+2stacks of Xeno for movement) > MNK(using the true max DPS rotation where you twin every 3 rotations so it changes a lot more) > NIN(although it's a lot easier than before the rework imo but it's still pretty tight) > BRD(procs galore) > SAM(realigning stuff) > DRG/MCH/RDM/MNK(using the old twin every other rotation so you always DK>TS making it easier to keep track of) > DNC.
For Healers it's fairly obvious I think, AST > SCH >>> WHM, and tanks I think are all fairly easy to execute and is mostly overall tank difficulty(repositioning, using cooldowns at the right time etc), although I guess GNB DPS rotation has more buttons to press than the other tanks and WAR has a tight rotation if you don't want to waste stuff(which can be a big deal since their DPS is so spiky around their short damage window).