I agree the Monk splash needs nerfing, but a Pal18/Mnk2 will be a force to contend with against Evil Outsiders. Having GEOB on any weapon they wield is pretty potent.
...but I'm not saying Monk splash needs nerfing, just the opposite.
With your example, Evil Outsiders, pure Pally will do significantly more DPS than Monk splash, and have higher Str and Cha too.
1 Monk is not a problem unless you bolt it on a Rgr.