I think it is actually just a known quirk with those putters. Have same issue with mine. On the 10 foot scale if on very fast greens I basically just have to hit it at the given distance. On fast greens it is even more difficult. I don't minus a foot for every inch and I add a foot to whatever is left over.Granted with my putter on fast greens with 8 ft and 3 inch dh I would have done like 7 feet maybe 8 but it would have gotten there. Thing is now you know. On a 10 ft scale just hit it hard, who cares if you miss and go by a couple feet, 2 feet coming back is easy; a 4-5 foot smasher on your scale.
You still have better precision forgiveness and balance then a starter. You just have to learn the idiosyncrasies. Most of the clubs have them and if you expect them not to and get mad that they do you are in for along road of stress, anger and not a whole lot of fun. Been there done that and still do it from time to time. Clubs aren't magical. A lot of times you need to spend a week or 2 with them learning them and once you learn them you would be surprised what you can do with them that you couldn't do before