OP, this kind of thread has been done for every job in the game at some point.... And it always comes down to the player him-/herself not doing it right....

Monks have the highest single target dps in the game if played right. They are useful in almost every encounter in the game... Their weakness is AoE, and therefore having several monks in one group can be hard in some encounters, but that's not the end of the world....

Learn how to play (watch a guide or something), or switch to an easier job.