Silver Wolf (银狼), abbreviated SW, is a punklorde hacker, aether editor, user banner, bubblegum chewer, and stellaron hunter. What Silver Wolf does has no equivalent in Genshin: she can implant a weakness into the enemy (for 2-3 turns). What this would mean in Genshin is adding an elemental gauge weakness to an enemy's shield or armor. So essentially a Fatui pyro shield could now take more gauge damage from say dendro attacks. But no character in Genshin can even do that.
Each of her attacks can debuff the enemy, reducing def, atk, or speed (for 3-4 turns). Besides implanting a weakness, her skill also shreds res to the particular element by 20%. Moreover it will shred all res by an additional ~10%. This effect lasts 2 turns. So she takes the role of universal res shredder at E0. Lastly, her ultimate will shred def by ~40% (can be leveled up) for 3 turns.
Imagine this in Genshin: you have a character that shreds res with E (ok maybe Morax), shreds def, atk, speed with each attack (who does this?), and then shreds 40% def with Q all at C0.
By comparison, Lisa's Q shreds 15% def. Pela's burst shreds less def and does not last as long.
A 40% def shred is around a 1.25 times increase in damage in Genshin. This becomes magnified considering Silver Wolf's other attacks can further shred def, and her skill can shred res (up to ~30% for a single element and ~10% universal res shred). Now 30% res shred is also around a 1.22 times increase in damage. So multiply the def shred with res shred, and Silver Wolf can increase damage (for all allies) by more than 1.5 times. This is comparable to Bennett's buff, meaning Silver Wolf is broken.
But it becomes even more broken when you realize that Silver Wolf's buffs are multiplicative with ATK buffs ('orthogonal'). So say you use Tingyun or Bronya to buff atk. Then Silver Wolf would provide an additional 1.5 times multiplier on top of the atk buff.
If Silver Wolf exists in Genshin, then you would have another Bennett that could multiply on top of Bennett's buff. So you get two 1.5 times universal multipliers for a total of a 2.25 times multiplier to all damage. So just by having Bennett and Silver Wolf's replica in Genshin, you can double the damage of most units in the game.
Her technique (which ignores weakness types) is broken, especially given that it is aoe, affecting all enemies.
For pure support build, one can prioritize effect hit rate and energy generation (to have burst up as much as possible). Still Silver Wolf herself can do decent damage so building atk, crit, quantum dmg is ok too if one has enough hit rate. Her F2P weapon (from the 1.1 event) is good for providing effect hit rate.
For teams, as explained above, SW is a universal buffer so she can fit in any team. In fact, she is perhaps more universal than Bennett as her def/res debuffs increase the damage for every character, whereas Bennett's atk buff may not affect characters that scale with other things like hp.
One team to highlight is the mono-quantum team of SW, Seele, and Qingque. In such a team, SW's skill will always implant a quantum weakness, so there is no need to bring any other element. The team would be complete once a quantum abundance or preservation unit is released.
SW's skill implants a random weakness based on the element of one of the team members. So in mono-quantum SW will always implant quantum weakness, which can accelerate the toughness breaking process. Even in non-mono situations, SW will always implant an elemental weakness that one of her team members can break, so the rng of the elemental type is actually not a big deal. Even though it is rng, there is a 100% chance that the elemental type weakness implanted can be broken by one of her team members.
E1 allows Q to regenerate up to 35 energy if there are 5 debuffs on the enemy (Q costs 110 energy). E2 reduces enemy effect res by 20%. E4 allows Q to deal up to 100% more scaling if there are 5 debuffs on the enemy. E6 gives SW up to 100% dmg bonus if there are 5 debuffs on the enemy.
100% dmg bonus is a lot. Xiao gives this much dmg bonus to himself with his Q. There are few abilities in Genshin, nevermind constellations that can give 100% or more dmg bonus to all damage. For comparison, Scaramouche's C2 only buffs his Q damage.
In the beta, according to rumors, SW's E6 allowed the weakness implant to last forever. While this is nice, one needs to think about how broken that actually is. The weakness implant from SW's skill lasts 2-3 turns (3 with passive), which is already long by HSR standards. Moreover, each time she uses her skill, she will implant a new weakness replacing the old one (or refreshing it). So it is not like she can stack more than one weakness on a single enemy. If it were possible to stack multiple weaknesses simultaneously on one enemy, then yes E6 would be even more broken, but also E0 SW.
The old E6 is also useful if you just want one particular elemental weakness to stick forever, rather than constantly have rng replace it every 3 turns. This can be useful if say you want a lightning weakness to remain on a boss so that Jing Yuan's lightning lord can shred the lightning toughness by a ton each time. But in something like a mono-quantum team, the weakness implanted will always be quantum, making an infinite-turn limit nearly useless for this purpose.
Lastly, she would like to use her skill every now and then to generate more energy to get her burst (for the def shred) as just basic attacking does not generate as much energy as using a skill (basic attack generates 20 energy whereas skill generates 30 energy). So in effect, SW will always be able to refresh the weakness implant by using her skill every 3 turns (which is not asking for much), meaning there is actually no point in having the effect last forever (as it will always be refreshed anyways).
The old E6 of having the effect last forever becomes more broken in multi-target situations, where one does not have to worry as much about keeping track of when the weaknesses on different enemies will expire.
But then again, something that would be more broken to begin with is just making SW's skill and burst aoe rather than single-target.
Anyways, the new E6 giving 100% dmg bonus is in some sense a buff for SW's damage (potentially turning even basic attacks into mini-nukes), especially in single target scenarios where SW would be constantly refreshing the weakness implant anyways, rendering infinite turn limit useless compared to just dealing more damage. In multi-target situations, perhaps the old E6 could be more broken. In an ideal world though, it would be nice to have both effects (include both effects, the infinite turn limit and 100% dmg bonus, as part of E6) or even add another effect: making SW's skill and burst aoe (like her technique).