I've recently started investing more towards warrior monks, especially naginata. Throw in a charge+war cry and all you see is routing ashigaru trampling over their fallen comrades...
I'm not very worried about warrior monks lacking armor, because most of the time they're clashing with enemy front lines so fast that half the arrows fired by the enemy are friendly fire. Though it's very lame/funny to hire warrior monks from a holy site province that gives +5 to morale...