Vs the elite soldier my monk build would need
AC: 13+
Ref: 12+
Fort: 18+
Do you see the problem here?
Vs the rats:
AC: 9+
Ref: 12+
Fort: 9+
Vs Gharash Vren
AC: 15+
Ref: 10+
Fort: 13+
Vs Archers
AC: 7+
Ref: 10+
Fort: 13+
Vs Outlaws
AC: 12+
Ref: 10+
Fort: 13+
I see some definite consistency in that almost all the fort attacks above are the worst to-hit for each creature. Gharash Vren (AC) and the rats (Ref) being the exceptions.
The numbers here show that there is nothing wrong with the monk at all - using his at will vs reflex attack he needs a 10 or 12 to hit all of the monsters in those encounters. With combat advantage that is a 8 or 10.
Either it was just a really bad run of bad luck, or someone was doing something wrong at the table. The monk character has roughly the same to hit as the wizard, there is nothing in the monk class or the way he has been built that would explain the amount of misses.