After a few months of module 16 being live and seeing nobody plays Whisperknife, and there are no guides for it here I decided to make one because I feel like the path is perfectly fine and actually very fun to play.
When module 16 went live i had over 300 respec tokens on my Rogue, I tried every combination of Feats Several times for Whisperknife and this is what I ended up deciding worked best for the way I play this class , I have 1 Assassin Loadout, which I don’t use and don’t even know the feats on.
<Feats>
1. Last Moments
2.Hidden Attacks
3.One with the Shadows
4.Shadow of Demise
5.Ambusher’s Haste
<Personal Powers>
Dagger Threat and Advantageous Position
~Combat~
<Single-Targets>
Q=Shadow Strike
E=Vengeance’s Pursuit
R=Lashing Blade
1=Hateful Knives
2=Courage Breaker( I actually do not use any daily Besides Hateful knives, this is just there to fill this slot!)
At-Wills are Sly Flourish and Shuriken Toss
<Multi-Target>
Stealth, then aim at the toughest enemy and throw Shadow Strike immediately followed by Vengeance’s Pursuit 2x, and then if there are more then 1 enemy, use lashing blade on whatever other enemy is nearby as Shadow of Demise will kill the first target, Dodge roll out of the way and use shuriken toss until your Stealth is back and powers are all off cooldown, then repeat the rotation above.
One nice trick is that Vengeance’s Pursuit is a power with a follow up and when the initial hit kills the enemy or if you hit them with something else and kill them the power resets, so you can go into stealth and then take out targets one at a time with it because you have Combat Advantage and also the initial hit does not drain any stealth, it will have no cooldown as long as you do not do the follow up attack, its tough to master but very fun to do.
<Bosses>
Soul Sight—>Stealth–> Shadow Strike—> Vengeance’s Pursuit 2x –> Lashing Blade–> Hateful Knives (if you got a daily up!) then this is the only time I use Sly Flourish and I use it to fill in the Remainder of my Shadow of Demise while I still Have Combat Advantage from Advantageous Position.
then dodge roll away from melee range and go back to Shuriken Toss as you wait for Encounters to Recharge.
<AOE>
Q= Path of the Blade
E= Smoke Bomb
R= Blade Flurry
1= Hateful Knives
2= Whirlwind of Blades
Start combat with a non stealthed Path of the Blade because it lasts 2x as long and then go into Stealth, roll right into the center of all the Enemies and use Smoke Bomb then Blade Flurry followed by a Dodge roll away from combat, use Shuriken toss and continue Dodging if needed, if Encounters come off cooldown, repeat the rotation above, or use your own discretion.
Whirlwind of Blades has some potential use for trash, but as trash dies so fast I feel it’s a waste of a Daily, but if you have to use it then do it at the start of the fight, stealth then Whirlwind and hope it clears the room, if not use Smoke Bomb–> Path of the Blade–> Blade Flurry and dodge roll away and toss shurikens until its over or you can do the rotation again 
^ this works best for AOE, but mostly I don’t bother changing powers up and will just use the Single-Target Powers selection for an entire dungeon.
<Companions>
I use the Owlbear Cub as summoned Companion and the rest are just for Armor penetration and Combat Advantage as this is not my main character so I do not spend much on her.
Companion Power is Potent Precision, when you attack there is a chance to gain 5% Critical Severity for 15 seconds (seems to stay active nearly 100% in combat)
2 Choke Chain of the Companion
1 Pearl Ring of the Companion
6 Empowered Runestones
<Insignia Bonuses>
Gladiator’s Guile and then any Defensive ones that work for you, I use Barbarians Delight and Revelry as well as Victim’s Preservation and Champions Struggle.
<Ability Scores>
DEX for Movement Speed and Critical Severity and STR for Physical Damage and Stamina Gain.
<Boons>
She doesn’t have many as you can see, I will eventually take all the Power and HP boons , Movement Speed (Tier 2) and Companion Influence (Tier 3), Action Point gain and Critical Severity (Tier 4) and for the remaining boons I will choose Combat Advantage and Armor Penetration, Blood Lust 3/3 for Master Boon.
<Gear>
Head:Hood of the Spy’s Guild (Yawning Portal seal Vendor)
Chest: Gurdann’s Defense (Master Expedition drop.)
Armor Enchantment: Shadowclad
Arms: Crash Guards (Master Expedition drop.)
Weapons: Alabaster (RNG based reward for completing master expedition)
Weapon Enchantment: Vorpal
Main Hand Artifact Feature: Shuriken Toss deals 10% more damage.
Off Hand Artifact Enhancement: Power and 10% Critical Severity.
Feet: Primal Assult Butisi (chult/barovia seal vendor)
Neck: Baphomet’s Infernal Talisman
Rings: 2x Ebonized Raid Ring.(ME chest reward or end reward)
Waist: Demogorgon’s Girdle of Might
Shirt: Restoration Shirt of The Spy’s Guild (seal vendor)
Pants: Ward Trousers of the Spy’s Guild (seal vendor)
Offense Slots: Radiant
Defense Slots: Slivery
Utility Slots: Dark
It’s not much, but I told someone I would do this guide…Enjoy 