I've been doing fairly thorough testing of runes for science, I'm that sad.
I wont go into the numbers and too much detail but reloading same environment vs same monster (leshen). ran with 3 runes of same type each time.
chernobog rune acording to dev post is supposed to increase attack power so x3 greater runes should be 15% attack power he claimed it was just UI is broken, however I tested it and UI is correct the rune has 0 effect in testing.
the fire DoT scaled with attack power strangely, the tick damage was lower but more ticks for more overall damage - really weird. Attack power also doubled amount of poison DoT ticks. I thought burning rune would be best, since against humans its does damage over time aswell as crowd control and alot of monsters are weak to fire. Fire dot also does its damage over less time than poison.
however I've changed by mind, the armour piercing runes are all around best pick imo. Don't get me wrong 15% burn, or even stun/stagger is going to be very strong. However +70 armour piercing increased damage by about 13% on both high and low attack power set ups.
It felt alot like the leshen would be poisoned alot less than burned, the % on the runes was simply does not seem accurate in my tests. which made me wonder if rune effects of same type stack, however with armour piercing the effects stacking is very noticeable. which is why I assume certain monsters resistances effect rate of poisoning/burning or even complete immunity. It does say in bestiary leshen is weak to igni.
The freeze chance also seemed felt lower than burning, freeze does not stop enemy like stun/stagger it only slows them down. but it does last a fair amount of time. However I can't be sure its the % chance to burn/poison/freeze my target are actually different, that would require way more science that I'm willing to do. However I never saw my stun runes do anything vs lechen, which makes sense since Axii did not work either - immunities are definitely a thing.
My point is tho that the armour piercing rune is going to be beneficial on every swing vs every enemy. sure some enemies have more armour so effects may vary, but less so than the other runes which might not do anything at all in a fight due to luck or foe's immunities.
Last caveat is that watching humans scream as they burn is probably more fun than any % in damage, but thats what the "pyromaniac" skill is for.
You basically switch targets by movement keys+looking their direction(like having them in the center of the screen), you'll get the hang of it.
this. the lock on system is bad and misleads the new player, since actually game works very well without ever locking on. character auto targets whichever enemy you move towards while swinging. that guy in video just simply hasn't figured out how to play yet.