Here’s a RQ guide to facesploding everything as WS and reaching the peak of her potential.
Melee Weapon
Lot of flexibility here but I personally recommend either SnD or Glaive. Both are extremely well balanced. SnD is a good all-rounder with great mobility, extreme attack speed, excellent up-close-and-personal horde clear, excellent flow, great charged attacks and block cancels, an excellent push-stab, and ideal attack angles while still being passable against armour. Glaive is also a good all-rounder that sacrifices a bit of mobility, attack speed, and horde clear potential to gain superior armour pen. Essentially, what one of these choices lacks in one category it makes up for in the other without totally sucking in any situation. Most of her other weapons are passable as well, however.
Properties and Traits: There are two ways to min:max WS’ melee weapon. Either go Attack Speed + Crit Chance + Swift Slaying or go Stamina+2 + Block Cost-30% + Off Balance. I personally prefer the more aggro approach because it’s devastating, lets you put out higher numbers, you will proc Swift Slaying constantly, and it makes you kill way more when you really need to. I also consider it safer because going full meatgrinder with her just protects yourself and other people when you’re surrounded far more than turtling does. That being said, even with the defensive spec’d melee she can still sufficiently shred, and stamina +2 + block cost-60% (with the necklace factored in) dramatically enhances survivability in extreme situations. This ultimately comes down to personal preference and both options have their merits. I tend to believe the defensive + Off Balance approach is the better one (Off Balance is OP af) but still use the aggro loadout myself because it’s just so fun and sometimes the best defense is a good offense (and because green dust doesn’t #$%ing exist).
Ranged Weapon
Just take longbow. The reasons for this will become more and more clear as we progress through the guide but it’s just, by far, the superior option. It’ll kill everything the other bows can and more but it’ll get the job done faster, harder, and more consistently. There’s some grounds to debate Swift Bow with a Hunter trait thanks to the better ammo regen but it’s still not as good all-round as Longbow.
Properties and Traits: Crit chance +5% + Crit power +20% + Scrounger. WS already has enhanced crit chance and crit power, so doubling down on the kit gives you a ton of power. Eg. You can and will routinely one-shot Maulers. Thanks to her maxed out crit chance, Scrounger is a very reliable way of maintaining ammo. Pro Tip: Scrounger also applies to Trueshot Volley 
As such, Scrounger isn’t abusive and you can/will run out of ammo if you’re not a lil responsible but it gives you sufficient sustainability that you can lmb spam into hordes until the cows come home. If they’re spread out to the point you’re not always hitting multiple targets, it’s probably time to switch to melee anyways.
Necklace
Health +20% + Block Cost reduction -30% + Natural Bond. If you’re going full-aggro on melee weapon, stamina +2 would be decent as well instead of block cost reduction. You can do stamina +2 block cost -30% but tbh, the extra health synergizes well with Amaranthe and helps compensate for the fact the game is still kinda a buggy mess and you’re just gonna take some hits for bs reasons you have no control over. As for Natural Bond, it’s incredible on WS because it stacks with Amaranthe and WS generates non-stop temp health regardless. Don’t listen to the naysayers. If you’re even remotely good, NB is extremely potent and worth consideration on characters who can quickly/reliably generate temp health to begin with. This is especially true in Legend where healing is more scarce. The fact WS already has innate regen is just icing on the cake.
Charm
Attack Speed +5% + Crit Power +20% + Decanter>Proxy. Again, doubling down on WS’ built in strengths, making sure crits happen more often and hit harder when they do. If you know your team comp going in, Proxy can sometimes be by-and-away the strongest choice here but since Kerilian benefits equally from all three pot types where other characters sometimes don’t, I suggest Decanter. If you’re popping a potion on Kerilian, it’s for a good reason and all three varieties make her an unstoppable murder-beast, so Decanter is just 50% more murder-beast and turns the tides harder.
Trinket
Crit Chance +5% + 33% Curse Resistance + Shrapnel/Grenadier. Don’t be a hero and try to get away with running Movement Speed or CD reduction instead of Curse Resistance right now. Again, as with taking health on the necklace, the game is too buggy to guarantee your skill is ever enough to compensate for the random janky crap that comes up sometimes and hits you when there’s nothing you could have done to avoid it. Eventually, the game will probably reach a state where Crit Chance +5% + CD/mvmt +5% is superior. There are solid arguments to be had regarding Shrapnel vs Grenadier but I don’t consider the Shrapnel debuff to be anything to balk at and it’s my personal preference. It also dramatically improves the value of Incendiary Bombs, where Grenadier does not.
Talents
MMMML: Most of these choices are self-explanatory or are already generally recognized as BiS but I’ll elaborate.
Morai Heg’s Scorn > Fury of Anath Raema >>>> Hukon’s Tenacity: Attack speed’s great but crit chance is more important as it synergizes with Scrounger to enhance sustainability and ensure more reliable performance against armoured targets like CW. Plus, her attack speed is already through the roof, especially with SnD, and more than enough to decimate any horde solo in melee w/o taking damage. Anytime you’re not spamming lmb attacks you’re performing a precision strike charged attack on an armoured target against whom you’ll likely have to block again right away, so the attack speed buff is going to waste there anyways.
Daughter of the Hunt >>> Arcane Bodkins >>>>>>>> Ironfeather Flights: Again, this is doubling down on WS’ top-tier crit chance and crit power. It works universally where Arcane Bodkins only works on headshots, making it considerably worse during boss fights where you’re just not gonna reliably land headshots consistently. Ammo on boss death is a pointless, trash talent.
Vaul’s Quiver > Isha’s Embrace >/= Rejuvenating Locus: Despite what some people think, ammo regen applies even when you’re above 50% health. With Vaul’s Quiver + Scrounger, you have the correct, best min:maxed amount of ranged sustainability without having to sacrifice anything more than you need to. Personal regen buff is a lil overkill as you’re gonna hit 50% very fast with vanilla Amaranthe + NB. Team regen is decent but the fact you’re entirely self-reliant when it comes to healing means more general healing for everyone else and the team regen isn’t gonna heal nearly as much damage as you prevent by never having to worry about ammo with Scrounger + Vaul’s Quiver. Rejuvenating Locus does work extremely well on Nurgles Rot deeds or no-pickup deeds where everyone is running NB as well, however.
Khaine’s Thirst. Obvious.
Asrai Focus >>>>>>>>>>>>>>>>>>>>>> Kurnous’ Blessing > Lifebloom Arrows. When given the choice to go full Yondu, always go full Yondu. You should be using Trueshot Volley virtually every time it’s ready, only pausing exactly long enough to aim it for max impact. Even if you can’t see enemies, just aim it where you know it’ll likely encounter enemies (avoiding areas where you know there are enemies you can avoid) and fire it. 30% more Yondu is better than the piddly few arrows you get from Blessing because Scrounger + Vaul’s Quiver already got yo back. The Lifebloom perk is trash because you’re already getting ridickadonk temp health vis-a-vis you’re basically The Wife from Kill Bill to begin with, but with a slaughter-bow.
Playstyle
(Note: Writing this for SnD or similar dual wield. If you’re rocking Glaive, be more aggressive vs CW and SV)
Pretty simple and self-explantory and a lot of it is muscle memory you’ll just have to feel out for yourself. Quickly/efficiently land headshots on SV and most specials. Go for body on Mauler. CW, if you’re the only one hitting it, you can handle just fine with ranged headshots but if it’s the fray, either switch to charged melee spam at the head while dodging or simply focus on everything to give your team more breathing room while the people specialized at CW murder do their thing. LMB spam into hordes until they get close enough to make melee the better DPS option. Weapon swap is smooth/fast on WS so never be afraid to strafe back and pop a few rounds into a clump to boost temp health and spike your DPS output. In melee against unarmoured, spam LMB while constantly strafing with a breath in between to keep from running out of dodges. If a SV is in the mix, keep doing the same but avoid his swings and perform one charge attack when there’s an opening, being sure to aim it such that you also kill the trash around him with the swing. The push-stab is also AP and has excellent range/speed so practice it and get use to using it in similar situations; it lets you sneak in some instakills or AP damage where you otherwise wouldn’t be able to.
You have the survivability to carry a grim if you want but since you make such good use of all three pots, it’s better not to. In order of priority, factoring in other character’s needs, you should choose Speed >>> Str=Conc. Kerilian really gets more out of speed pots than any other character so be a bro and leave the concs n str for the classes that need em in order to min:max their rampages. If you have someone like a BH or Pyro, you’ll prolly just wanna mule a conc/power pot for them though if you happen upon a second one.
Get used to doing charged shot followed by light shot. This is the best way to max spike damage eg. against a Leech.
Note: I will likely test a bit with crit+ and cd+ on trinket just to see how potent it is but I still encourage people to use curse resistance in general, due to the janky game behaviours that result in unavoidable damage at times.
Special Cases:
Shielded Stormvermin - If dealing with 1-2 w SnD, spam LMB. It will break the guard faster and kill them faster than charged attacks in general. If grouped at range, try to time your RMB lb attacks to coincide with them opening their shields up.