Why is the Monk so disproportionally difficult to play in comparison to other DPS?

[Garnatian]

What does the Monk get in return for such a difference in difficulty?

As far as I am aware, the Monk isn't the best DPS and as far as melee DPS go, most people seem to favour Dragoons.

Also, can someone explain to me why there isn't an ability, say on a 60s CD, that gives max Grease Lightning stacks. It's like having the setup of a DoT class that takes 16s to cast all his DoTs.