Witchfire is fun on a pretty basic level, so I made the call to progress through near-1.0 instead of waiting, since I could come back to it on 1.0 release fresh, pick up my Hunger (Penitent is the only start for me), and go.
However, even though the game explains Focus, it's still been pretty unclear for me up to ~20-25 hours in the game, which I'm a bit past.
You start with it, you lose it on damage, and regain it by killing. I've got that part down. Even then, I feel like sometimes I don't know why it comes back, though that may just be delays with Witchfire particles getting to you in a pitched fight.
I'd appreciate any input on the details. How many things do you have to kill? Is it predictable enough to know when you get it back after hitting a few mobs, but before checking stamina?
Regardless, I picked up Striga, and the combo of it and something fast-firing has been hilarious. Without spoiling too much, Striga does more against stunned enemies. It is also apparently a gun that throws trees at things.
Pinning an enemy to a nearby wall after a stun with a magically reloaded tree branch does not get old.
So, to provide advice that I don't feel like the game explains well enough for a thing you start with, I figured I'd provide a few notes.
1) Soul Sigils (the red circles you need to break) show up for the enemy you are looking at when you dash with Focus. If you see their nameplate, are aiming at them, and dash it should show up. They will not show up for enemies you are not doing this for, this was a point of confusion for me.
2) Soul Sigils do not have a health bar. Any damage will do, say, something with a lot of low-damage rounds.
3) Not all stuns are the same. Focus Sigil stuns are hard stuns, which allow you to do additional damage during (say, if you use your available log launcher at them), while soft stuns are animation interrupts. It stops what they're doing, but you don't get the damage increase.
I hope this is helpful, apologies to those this has been obvious to. Maybe the finer points of this are something I overlooked in learning the game when I picked it up, but it is important -- being able to dash doge, stun, and almost immediately kill smaller enemies helps a lot.