I played a char awhile back that got destroyed by an assassin. My firth thought was "That's BS, they are overpowered". Then I played a couple for the first time in years. They are strong, no doubt, but my new rule is: Don't fight assassins when they are in Martial Trance. Flee. They can keep it up for ~5 hours a day. I can kill them when it's down.
I suspect monks are the same, and like most builds, the key is not to fight them on their terms. If they come after you, do not engage them. Give them the run around and when they stop pursuing you (because their spells/powers/etc. start to fall), turn on them and kick their ass. Better yet, attack them when they are otherwise occupied. Find out where their shrine is or where they buy food and catch them off guard. I have played plenty of chars whose power was probably overrated by my foes simply because they never got to fight me unless I was fully prepared for battle (spells/skills/powers/EQ I carried for their class/weapons best suited to fight them/etc.). Had they caught me once unprepared, they would have been bewildered by the difference in outcome. And, no, I don't play like that much anymore. Anyway, enough said about that.
I will admit that in the past people have complained about overpowered classes, been given the "you just don't know their weaknesses yet" and, in time, been proven absolutely correct when the class gets severely nerfed. The first few iterations of Major air forms come to mind, but there have been plenty of examples.
If it makes you feel any better, my level 15 cleric cast blindness on a battlerager that was fighting someone else and took an UNSPEAK from spellbane. From a blindness spell. At level 15. Now THAT was bullcrap. And I didn't even have anywhere to complain about it because there were no CF forums. I'm still pissed. I mean that's BULLCRAP!