The only passwords it makes any sense to ban are the fifty or so most common, plus simple number and case permutations of these, and MAYBE the most basic leet-s

The only passwords it makes any sense to ban are the fifty or so most common, plus simple number and case permutations of these, and MAYBE the most basic leet-speak versions as well. That's enough to make a prankster typing at a keyboard give up, and that's as much as you can hope to stop with this type of policy. No password ban will stop someone with a cracking app, and no serious intruder will be without one of those.