Absolutely stick with it! I created an exactly identical monk as Sensuke had suggested in one of his videos and had the same doubts.
Up until level 4/5 she was squishy as hell (going unarmed, only some cloth with 2DR and -5%). But somewhere around level 6, especially when you acquire a second tank (I didn't create any additional npc's, went only with the in-game ones), she started to show her value.
Eder and Pallegina are locking the first wave while the karate-chick runs around them and engages the casters and archers. Seriously, this looks hilarious cause she can interrupt any spell (skill 2/encounter) and if they actually manage to wound her they start flying across the screen :D I can't give you any statistics right now, but it really looks like she is killing half of the opposing force before others bring one or two guys down ; )
And I didn't even try to enchant anything yet so she's still running around with base stats.
Somewhere inbetween I tried to give her two spears but it felt like armed combat was pulling her down.
edit. oh and I played 'hard' from the beginning.