The Icy-Veins guide is largely considered by the community to be the superior option when it comes to hunter guides.
Here’s what it says about 4 set:
With the 4PC Tier Set Bonus, you should ignore Precise Shots and focus on maximizing Aimed Shot casts.
You could also go run a simulation and look at what the sample ability usage looks like. People have spent a lot of time optimising the APL to yield the highest number possible and that’s pretty much all the math being done for you, no need for a napkin.
But all of this is getting beyond the original point of this thread. There is no actual way to track the focus counter in game so we’re left guessing. And with the fact that said counter resets almost seemingly randomly as there is no consistency in what does or does not, this can lead to desynchronisation. The concern has been voiced by Jayeasy, the author of the tracking WeakAura, in the set bonus thread.