Looking at the masteries for cunning and ferocity

I dont understand why piercing thoughts and battering blows are separate, but yet precision is essentially the combo of the two just scaling instead of flat. Just from a common sense stand point should you be choosing between scaling or flat on the ferocity, instead of having it included on the cunning tree, yet split on the ferocity.

As the masteries stand there is no difference in choosing between 12/18/0 and 18/12/0 on the fifth tier and the only major difference is in cunning you get extra CD. There should be a meaningful difference instead of a "which keystone do you prefer"?