In both cases, the decrease you quote is about sqrt(10). It does taper off when you do a 24 character password (which is about the range of what I would choose)

In both cases, the decrease you quote is about sqrt(10). It does taper off when you do a 24 character password (which is about the range of what I would choose), but it's still 30%; 70% of a large number is a large number. Typical users are not so technical as to use a 24 character password and therefore, in an unsalted leak, after the rainbow tables stage, it makes it 30% easier to brute-force them (going by your numbers).