Once you see the equation its easy to figure out what is wrong with blunt mastery but tbh you dont really need to nerf blunt mastery if you are on a pserver if you just control the gear properly.
The bulk of blunt mastery's damage comes from this outdated multiplier. If the gear in a pserver stays within 500 int points (including alm and alm scroll) of the divisor blunt mastery will be balanced. I am a firm believer that pservers shouldnt encompass lvling (you start at max lvl with entry lvl gear and you do tasks/pay/farm to get better gear) so if they want to make stronger gear they can always double the divisor (meaning you need 2100 int to get a multiplier of 1.1 instead of 1100) and not have to worry about the consequences low lvl chars would face. Is that hard to understand? its the only reason int twins are decent since 900 inflated magic would actually turn into 225 magic if the multiplier didnt exist.