Archer's focus now kind of works like it says in the text, however the result of it now working as intended makes it exceptionally hard to utilize.
First, any movement now removes the focus buff that allows you to start gaining stacks and it takes around 5 seconds of standing still to get the buff back and allow stacks to start accumulating again.
The stacks themselves have a three second duration which with Rapid reload and Rapid fire on a repeater build is just enough time to get the next shot off before you lose a stack. When fully stacked you get a nice 30% damage boost to your ranged attacks.
Also, I am uncertain under what conditions, but often times after moving the entire stack will vanish. So the only time this ability can ever be used effectively is when not moving at all. I just can't find very many instances of ever being able or allowed to do that. Shooting a portal is about all I can think of.
Is that it's intended use? To augment ranged portal destruction? I had hoped it was meant to help augment ranged damage in general but that is definitely not it's practical use. You can't keep up with a group, you can't move out of the way of spells or dodge, all of this makes the ability inconsequential in the way this game has to be played.
If it's just meant to kill portals, fine. But if it was meant for more, it would be good to re-evaluate it as it is definitely lacking now. I had originally thought it was meant as an alternative to the Improved Precise Shot, giving an archer the option to toggle Archers Focus on instead for greater single target damage at the cost of being able to hit groups but the reality is that you can't do much to leverage the ability as standing still in this game is rarely ever an option.
Just some food for thought.