The teaching of so-called rules of thumb like the 3:1 rule are bad practice and lead to tactical group think. They do not aid tactical thinking at all, they actually hinder it.
Ken, you're so right on this one, the 3:1 madness that has polluted our thinking is destroying a lot of good options. The 3:1 metric was designed for a frontal assault against a peer enemy, so if our officers are still no better than they were in WWII Italy where they simply throw mass against mass, then hell we may need 10:1; however, if you're better trained, equipped and no how to maneuver forces you probably won't need a 3:1 advantage. This is group think at its worse. So typical of our force to look for simple rules to do their thinking for them, instead of actually thinking on their own.