Actually the first workout I ever did was 10-8-6 or something like that.
Bottom line for me was always effort. One in the tank ain't bad, but if I could get two more it was time to move the weight up. I'm not much for calculators in the weight room. Anyway, yeah its a fine idea and there are lots of variations. Like 5-3-1 has the ancillary work in the higher rep zones.