Welp, I'm confused.

[7h3C47]

Like most hunters at the cap, my crit rating has been maxed, and passively my/our ranged crit chance sits at 30%.

Entering camouflage adds 50% ranged critical chance, and the tool-tip changes to 80% accordingly.

On top of that, when you pop improved focus from camouflage, which adds an additional 25% ranged critical chance for 5 seconds at the conclusion of the skill, the tool-tip literally changes to 105%. See: http://i.imgur.com/7v7gsbH.jpg

And yet, I shot at a training dummy in DA 10 times doing this, and only 3 out of the 10 critted during this period of 105% ranged critical.

My head hurts.

[Giliodor]

You're doing something wrong, then. I always use Swift Bow from stealth, with focus, to make sure all three hits crit. And they always do.

[Gabli]

Actually, there has always been a bug in the way skills are queued.
Basically, if you queue an induction before the channel of "Focus" is over, the queued skill will not benefit from the buff (critical chance and critical magnitude). The way around it is to wait just a little after the channel is over before activating the skill.
You'll have the same sort of bug with RoA on-crit reset, if you use RoA to soon after Focus channel, it won't reset even though everything crits.

To sum up : the buff works, but don't queue you skill before it's done channeling. I'd advise to manually cut the channel (clilck/key the skill to interrupt it, or move a step) as the down time between interrupting "Focus" and firing your damaging skill is enough to make it "work".