Great post Avi.
It can be a very difficult to nail a grind setting. Especially when you have a blend which has some light and some dark beans or some larger or smaller there are so many factors present, the grind setting is hard to predict.
You can also get to the same shot by a number of different routes. A finer grind lighter tamp or coarser harder tamp can produce a 60 ml shot in 25 - 30 secs. Whilst both produce the correct time volume relationship the taste can be quite different.
There are just so many variables in producing a good coffee it can get a bit overwhelming in the home environment where you only produce a limited number of coffees per day and hence can only ever get to play with a few of the variables. :)