Salem

So, my group obtained a 13% pure dowsing rod. My mines and mountains proficiency has no effect on my ability to use a high % rod, does it? Or does this simply mean my immediate area has no mines near that level of purity? mean, we need to move closer to the darkness to get to that level of purity

You dont neccessarily need to move closer to the darkness. Keep looking around and although there might not be one as close to your base as you had hoped for, you will find one eventually.