A lot depends on virtues. Not all of the virtues work for monks fully. But at the end of the day here is how I would fight a monk:

1) maladicts matter, they seem like they don't, but a monks avoid is severely nerve after boneshatter alone. It may not see, like it, but it does. Dex way more than str... but get both if you can. Assassin who lands kans and kote and axe kick is going to make a monk run most of the time.

2) damage is king. Hit vulns without exceptions, if you aren't hitting caps damage on a monk, you should just leave and come back when you can. Use axes, flails, whips, daggers(nodisarm, daggers are ridiculously easy to respond). Avoid has des and weapon knowledge components.

3) dispel, even if your a mage, strip the extra protections and preps.

4) attack mana, if you can, but be careful, and be sure you can get it. Energy drain was almost useless against hunsodin. But stack plague before you do, and get sneaky about it, and you can catch them.

5) nerf his da,age output. find prot vs holy, and elements if you can. Realize a good monk is going to know you have it and switch to light based attack if he can.

After those it's about timing. A good monk will time intensifies for when you miss a bash. Trip wth cheap shot is better if they aren't flying. Lag moves like pincer are good, overhead opening is good. There are a lot more. People can post logs of beating me and you should see some good examples of what to do.