The problem is, if you have a bunch of partial passwords 1, 2, 3; 1, 2, 4; ... you can just brute force three character combinations of the passwords, which just takes something half a second (times the number of rounds) if you write your password cracker in bash. So your complexity goes from 52^n for a n character password consisting of lower and upper case to n/3* 52^3 which is a lot more manageable.