The point made to me, and why I chose to do it finally, was if your % to hit is over 100, then it doesn't matter if you give up a little of that, since 100% to hit means you always hit. This may not be true, but it did convince me that increasing the % crit was worth it. However, in boss fights I end up whipping out my best DPS weapon which is not a custom bow. Snakespeare is a bird. Your mileage may vary.