I had previously made a post that could be useful to include here:

RE:Bring back "Too weak to be worthwhile"

In FFXI, I found it very useful to determine the worthiness of fighting monsters for sp, by their "con". easy prey would give a basic expectation of sp on an easy mob, but was not considered too low to be considered a "trash mob". Too weak to be Worthwhile was used on monsters that were just that, a trash mob.

I suggest we add a new tier for monsters below blue currently in game. It can be gray, to indicate one will likely earn less than ~60-100 sp a kill