Mnk is definitely one of if not the fastest job at max level. It does have a lot of positional requirements for good damage but is fun if you like a combo master job. Keep in mind it will likely get a big shakeup in November. As said above Mch feels fast due to all it's oGCD where you're basically always doing something. Try everything out, see what you like. That's the great thing about FFXIV vs other MMO. You're not limited at what jobs you play. Unless you're Blue Mage.