What people fail to realise when they whinge about Warrior Monks in particular, and a few other classes in general, is that when you get a character played well they are unbelievable.
I too have seen W/Mo tank 3 other warriors for what seemed like eternity, iv seen monks that keep teams alive no matter what you do to one of their teammates, iv also seen Necro mesmer builds that completely destroy any character if they are left alone for too long.
The variations in effects you get in this game, from what little I have seen, is mindboggling. If you get good players playing with clever builds you can see some really cool things on the battlefield. You can make near unkillable characters, you make characters of near instant death, you can make characters to disrupt entire teams constantly and cleverly, characters to constantly maintain a team in perfect order, characters that can brutaly slay you from miles away.
Any nub, and I mean this, with the misfortune to take their 'uber god tank of swordmanship doomz0r' into a fight with some good players and clever builds is going to limp out having been owned, and probably come crying here to complain of imbalance. I myself have not seen anything that seems imbalanced, the difference between beating 3 warrior monks and a monk backup depends entirally upon what your team can do together. If your teamwork, skills, and build arent up to the test, you will lose. It might be your fault, it might be other fualts, that fact is you lost against other players, so go learn some more stuff about the game