I can understand that the muscles of the Rotator Cuff group are small and therefore I could understand the recommendation of using much lighter dumbbells *in relation to* other exercises. But almost in any site I have found, the recommendation is to *always* work them with the lightest pink dumbbells and in the >15 rep range.

Isn't that wrong? Why not to strengthen that small muscles by working them with sets of 5 reps too with increasing weight?. For instance, a rule of thumb such as *"use one tenth of the weight you use for the overhead press*" or something similar would be very interesting.