Despite having a low accuracy, with DEF being high enough, and shop guards being very basic (much like that of the zombie), I have nothing to worry about. Sure there's a lot of "miss" popping out of the shop guard and a lot of 0s popping out of Renya, I still level up a lot while also getting a ton of GP (yes, you're seeing that right, 203K per guard). I'm also getting equipment to burst so I can strengthen it a lot in the caravan, saving GP. I actually spent so much time doing this that I gained nearly 150 million total GP.