yours were 20-45 .... while melee was doing 60-80. were both of you usingthe same attack weapon? (slash,bludgeon,or pierce) who knows maybe you were hitting someone with your fist and he monster had high resistance/immunity to bludgeon and the melee class was using a weapon that bypassed or was not the resistance or immunity of the monter he was attacking. and were you STR based same as the melee one?
/me takes out my manual ....
Monks Bludgeon attack at Lv20 will dish out the highest damage than any weapon (1d20 / 2d6) [1st number is done by med/large , 2nd number is done by small]
highest Bludgeon damage on weapon is done by a Heavy Flail 1d10 (19-20/x2) .... thats 1d10 short from a Lv20 monk(fist) which would deal 1d20
again i made a comparison on beings that roam around planes that are mostly sneak/crit immunes ...... thus MONK still does more damage on bludgeon..... now if the "being" has resistance/immunity to bludgeon. thats when you take out your Kama ... and with Kama you still can attack more often with slash damage thus dealing more damage per round as compared to other melee class.
Flurry of Blow will give you an extra hit. Monks can do 5hits while other melee class only get 4hits. My Lv30monk does 6hits when doing Flurry of Blow (maybe due to the fact that i multiclassed after Lv20

) so that doesnt count as a pure monk ..... BUT fact still remains that a Monk can do 5hits while others only 4hits ..... thats an extra 1hit. thus killing opponent 20% faster than other

. am i wrong on this part?
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with regards to the AC about monk. i did mentioned Unbuffed

now imagine if he was actually buffed. Monks gain AC with wisdom modifier right? pair him up with a High caster Level druid and give him Owls Insight (wisdom = 1/2 caster level)

. the Monks AC doesnt stop there. at Lv18 monks get to cast Empty Body (50%concealment bonus) and am pretty sure everyone loves that. its like ii
with regards to Monks Speed +10% every 3levels after 20 if am not mistaken. so ... huhm a monk at 35 will have what 200%? heck no hasted class can chase him except another monk
sorry for the OUT-TOPIC.
Back to topic. Like fatzo said theres no way to chase a high level monk since he only goes to that tunnel (what ever that is sorry no idea since i dont play much on main). unless i think if you lay loads of traps on that portal

and wish he trips on everyone of it and hope it actually works.

but what Amoenotep said puzzles me "they are dwarves and dig in the dirt" ... i wonder if they cover it as fast as they dig it

kidding.