Fan of Knives:
There are a lot of questions involving Fan of Knives, and how it interacts with different weapon types and poisons. The tooltip indicates that it deals 100% weapon damage with most weapons, and 150% damage when you're using a Dagger. However, that's all the explanation that we receive from Blizzard's end. In order to maximize your FoK damage, which becomes crucial on AoE fights like Yogg-Saron's hard modes, weapon selection becomes paramount.
Daggers vs. the others:
Daggers receive a hefty 50% boost to the damage the deal via Fan of Knives' inherent bonus. It's important to mention that FoK calculates its damage on a per-hand basis. This means that if you use a Sword in your Main Hand and a Dagger in your Off Hand, only the Off Hand portion of the FoK receives the 50% bonus, and vice-versa. This is also true for Poisons: the poison on your Dagger receives no 50% bonus from FoK. If you use two Daggers, both hands receive the boost. I tested using Kel'Thuzad's Reach / Hailstorm for my MH/OH and Sinister Revenge as my experimental dagger.
Off hand penalty:
While the 50% bonus from FoK did boost my Sinister Revenge's damage, the Off Hand FoK attacks are affected by the Off Hand Weapon Penalty. This means that your off hand FoK attacks will only deal 50% damage, or 75% damage with Duel Wield Specialization. Therefore, when using FoK, be sure that your strongest weapon is sitting in your Main Hand. I believe the formula is such that an Off Hand Dagger attack with Dual Wield Specialization (which nearly every spec has) deals 125% damage, as this was consistent with my results.
Poison proc rate:
Due to the new PPM mechanic for Poisons, slow weapons have a very, very high chance to proc our poisons. The chance for Wound Poison to proc when using a 2.6+ speed weapon is around 95%. However, our chance to proc with a quick weapon like a Dagger is far lower. This means that even though Daggers may be doing similar FoK damage as slower weapons, they will proc far fewer poisons when using FoK. This means that Daggers are universally bad for FoK, as are any quick weapons like Hailstorm. You'll want to equip your two slowest weapons and coat both of them with the poison of your choice. Wound Poison is the best call for Combat, while Instant Poison reigns for Mutilate. Deadly Poison is also an option if you're sporting 2 pieces of our T8 set, as the bonus can flood you with extra energy.
Speaking of energy regeneration during Fan of Knives spamming, currently Focused Attacks is the only method of returning energy that works on FoK attacks. However, in 3.2, Blizzard is changing Combat Potency to include all off hand attacks, which should include FoK in the energy return bonus. This change alone will boost Combat specs' FoK damage by a very significant amount. Because Assassination can't pick up talents like Throwing Specialization and typically tend to revolve around Dagger attacks, Combat has been the go-to spec for Fan of Knives-spamming Rogues. Vile Poisons is about as deep as the typical Rogue will go into Assassination unless they're going all the way to Mutilate.
Another reason that Combat Rogues are suited for FoK is the synergy between FoK and Blade Flurry. Blade Flurry will replicate the Main Hand (and Main Hand only!) portion of FoK onto a nearby target who was NOT the target of FoK. Imagine you're standing near a Mage and Priest, and you use Fan of Knives. Your Off Hand attack will hit both, and will likely proc your poison on both. Your Main Hand will also hit both, and will again proc your poison. The Main Hand attack that hit the Priest will then replicate onto the Mage, and the original Main Hand attack that hit the Mage will replicate to the Priest. That's like dealing 4 Main Hand attacks, 2 Off Hand attacks, and 4 possible Poison procs off of a single attack!
Killing Spree and FoK combo:
What I like to do in heavy AoE situations is to pop Blade Flurry immediately, and use all of my energy to spam FoK. Once I'm completely drained, I'll use Killing Spree (which is also affected by Blade Flurry!), and then finish with a few more FoKs with the energy I gained while in the Killing Spree. This will yield massive AoE damage, considering nearly every attack will proc your Poison of choice and you're hitting with two very slow weapons incredibly often.
Throwing Specialization adds a very clutch interruption effect to the attack. This can be key on fights like Vezax where you may miss a Kick on an important Searing Flames and be required to use another attack to interrupt the cast. It's also great for PvP, allowing a Rogue to effectively reduce his opponents to only using instant casts while he is nearby. If you have room in your spec for the talent, I suggest taking a look at it. It's going to decrease your DPS, as you'll have to sacrifice an important Combat talent to pick it up.
Fan of Knives is immensely powerful, especially when used properly with two of the slowest weapon you can find (no daggers!) and your strongest poisons applied. Couple that with your cooldowns such as Blade Flurry, Adrenaline Rush, or Overkill: you've created an AoE killing machine. A quick use of Tricks of the Trade later, and you've become the threat-generating tool that tanks will fight over. Good luck explaining to the Shamans in your group while you'll be rolling on The Stray, though!
Are you a Rogue looking to up your game? Check back every Wednesday for the latest strategies in Encrypted Text! And for the raiding Rogue, get ready for Ulduar with Ready Check and our Ulduar guide for Rogues, parts 1, 2, 3, and 4.