I think the monk works best with a druid in the party (for barkskin and magic fang). A monk takes very careful and creative playing to be truly effective, so without a particularly knowledgeable and creative player, bolstered by a friendly druid, I think it's much harder for a monk to be effective.
The other classes offer much better off-the-cuff firepower, muscle, or skills that don't require as much thought and planning to implement.
The other classes offer much better off-the-cuff firepower, muscle, or skills that don't require as much thought and planning to implement.