Here's a detailed guide for those who wants to be a Witch in Skyforge.
Ideally, your stat priority is: STR > Luck > Crushing Blow > Accuracy > Crit > Temper. This provides you with the largest amount of up-front damage through having your Taint, Explosion of Darkness, and Murder of Crows being buffed by Accuracy (which is directly influenced by strength) and having them crit at the same time, as well as proccing Crushing Blow on the target.
If you have the double chapel items from the Law and Order event, you'll want to ideally use them on the two provinces that give you both Crushing Blow and Critical Chance, however in future patches this may change, in which case your items will be refunded allowing you to use them a second time on any major stat rebalancing. You can also use one of your double chapel items on Dawn Plateau, as not only does that province have both Accuracy and Critical Chance, but it also has a Temper chapel as well.
You'll want the mainhand with Taint damage.
Your offhand will be the Murder of Crows duration increase.
Note that you can also use the offhand that reduces your damage taken while channeling Dark Ritual, and keeping one in your bags is highly recommended.
Your rings should be STR/Luck/Accuracy/Crit, or the Deft Assassin's Signet.
And your amulets should all have the increases for Explosion of Darkness and Murder of Crows.
The most important symbol slots to have here are Maximum Recoil, Ultimate Strength, Warrior's Creed, Compressive Trauma, Lacerated Wound, Mark of Death, Cold Calculation (Archer), Gravitational Perturbation (Kinetic), Strength Serum (Alchemist), Jinx (Witch), and Divine Intervention (Paladin).
The rest of the symbols that you use can be personal preference.
The Element of Surprise symbol is extremely good in short fights such as clearing trash or Squad/Group bosses, however it becomes almost obsolete once you get to distortions. In those scenarios, you're much better off using a talent like Rapid Attack.
Lucky Shot is another talent that is quite good, however once you get full Critical Strike rings, it becomes almost pointless to waste a talent slot on because you'll only be gaining a very minimal amount of crit.
Painful Spasms and Deep Dissection, the other two on-hit DoT effects, don't scale nearly as well as Lacerated Wound and Compressive Trauma since you'll rarely be using Valor or Spirit for right now, however it's extra damage and there aren't many other symbol slots that you'll actually need.
The same applies to Mobilization and Impulse Intensity, as well as Pain Shock. They're minimal damage increases but damage increases are still nice.
As for other class symbols, the Berserker symbol is extremely good when you're doing solo play and actually taking damage, however in Groups and Raids, it is relatively useless because proccing the Berserker symbol will mean that your Lightbinder and Slayer symbols, if you have them, are useless. Both the Slayer and Lightbinder symbols are extremely good, but require you to be good at dodging mechanics and taking as little damage as possible, because any damage taken will cancel their effects.
Taint is the ability that the entire Witch class revolves around. It is a single target Damage over Time effect that also empowers your other abilities.
Epidemic basically just spreads your Taint in an AoE, and increases the size of your Murder of Crows. This is your main way of doing AoE DPS through spreading your Taint to all targets.
Murder of Crows is an AoE that you place on one target. If that target dies, your Murder of Crows is cancelled, so make sure to put it on a target that probably won't die before it's full duration is over.
Dark Ritual is a channeled ability that restores your mana, which is great to use during your downtime between Explosion of Darkness casts.
Bewitch is a directional taunt. Only use this in rare situations if your tank is having problems with taking damage, and make sure to kite during the taunt.
Envoys of Taint is a single-target damaging spell. You accumulate charges of it passively and can activate it to discharge all of your crows at your target.
Really simple, reduces the damage your target does. It's not useable on bosses though.
Ahh, Volatile Curse. The one spell everyone hates us for having. Basically, all this spell does is puts a massive shield on the target. If your group breaks the entire shield during the duration of Volatile Curse, it does a lot of damage... and by a lot. Also, please note that using Volatile Curse while another is still applied will cancel out the first curse. This means that instead of breaking two curses, you’ll waste the first and only potentially break one (if you can even break it after wasting your burst).
Similar to Bewitch, Racket of Crows is a directional spell. It does damage to all targets in whichever direction you aim it, applying 3 stacks of Taint to them every second in addition to dealing a large amount of damage.
Killer Crows is a single target damaging ability that does more damage depending on how many stacks of Taint you have on your target.
Like Killer Crows, Explosion of Darkness is a single target damaging ability that does more damage depending on how many stacks of Taint you have on your target. However, Explosion of Darkness consumes your stacks of Taint, and is by far your highest damaging spell outside of Volatile Curse.
Extermination is basically identical to Explosion of Darkness, except it's an AoE.
Ring of Fire is a placeable AoE (Similar to Cryomancer's Whiteout) that does a large amount of damage to anyone inside the circle. However, when you use Ring of Fire you'll be put on an extremely long cooldown to use any other spells (except Explosion of Darkness and Extermination) because of how long the casting animation is.
Last but not least, Living Helper. Please never touch this spell. Never.
Honestly, Witch is a pretty simple class to play. 75% of your time will be spent reapplying taint and waiting for Explosion of Darkness to come off cooldown while spamming Killer Crows. For the most part, there are only five abilities you really need to worry about; Taint, Murder of Crows, Envoys of Taint, Killer Crows, and Explosion of Darkness.
When starting a single target fight as Witch, you'll want to hold your left mouse button and fully channel Taint. This will apply Triple Taint, which applies all three stacks of Taint at once. However, the ONLY time you want to use Triple Taint is at the very start of a fight, because it is faster to apply Taint three times than it is to fully channel it.
After applying your three stacks of Taint, you'll want to use Murder of Crows. Now, if you're supposed to apply the first Volatile Curse, you'll want to do it now. The reason you delay applying Volatile Curse is to allow the rest of your DPS to set up their buffs. For example, both Kinetic and Berserker have a small amount of time of applying self buffs and starting their combos to apply maximum damage into the Volatile Curse shield.
After you apply Volatile Curse, you'll want to switch to Extermination Stance. At this point, you cast Envoys of Taint and then use Killer Crows once followed by Explosion of Darkness. You ALWAYS want to use Killer Crows before using Explosion of Darkness, because Killer Crows will proc your Impulse charge which will proc Kinetic symbol for 10% more damage on your Explosion of Darkness.
After using Explosion of Darkness, you'll want to apply three stacks of Taint again. From now on, your rotation is just a rinse and repeat. After you apply Taint, you'll want to reapply Murder of Crows if it's off cooldown (channel Dark Ritual for the mana to cast Murder of Crows if you do not have enough), and if not you'll want to switch back to Extermination Stance and spam Killer Crows until right before your Impulse charge comes off cooldown. Right before it comes off cooldown, switch back to Curse Stance and reapply Taint once to refresh it to the full duration. Then, swap back to Extermination Stance, cast Killer Crows once for Kinetic symbol, and use Explosion of Darkness.
Your actual rotation during the fight would look something like:
Taint x3 > Murder of Crows > swap to Extermination Stance > Killer Crows > Explosion of Darkness > Taint x3 > swap to Extermination Stance > spam Killer Crows until Impulse Charge is off CD > refresh Taint > Explosion of Darkness, repeat until target is RIP.
For fights with more than one target, you'll do almost the exact same thing except instead of using Explosion of Darkness, you'll use Extermination. Also, after applying three stacks of Taint, use Epidemic to spread the Taint to all nearby enemies. During AoE fights, you'll also want to use Explosion of Darkness on your main target inbetween cooldowns of Extermination.
The actual fight would look something like:
Taint x3 > Murder of Crows > Epidemic > swap to Extermination Stance > Killer Crows > Extermination > Taint x3 > swap to Extermination Stance > Explosion of Darkness, repeat until there is only your main target left and then go back to a single target rotation.