As the title.

a monk (pure or multi) is the only effective decoy in HoF, meaning a char to rush in and have the monsters gather around him. then finish them with monk and your others.
my opinion comes from the possible highend AC a monk can have. i have read a description to create a multiclass monk with AC 87 ...

Since this IS HOF we're talking about, I'd say take one, they're quivering palm ability can be usefull in a fight where you need a quick slaying