These days the setting may well have been depreciated. Back in the day it was popular because AF was either non-existent or prohibitively expensive. Now with 16xAF basically only incurring a 5% performance hit, there?s really no point to a negative LOD.
AF, unlike a negative LOD, increases texture sharpness without introducing texture aliasing, so it?s always more desirable.
Have you tried the texture mip-quality slider in CCC? Setting it low would probably approximate what a large positive LOD would do (i.e. it?ll make everything blurrier and increase performance).