In the Wrath expansion rogues got Fan of Knives at level 80, giving us a true AoE ability. (Blade Flurry is not a true AoE since it can only hit two targets no matter how many are nearby) It even procs poisons, so we can hit everything around us with both weapon and poisons for a satisfying burst of numbers exploding on the screen.
Unfortunately, it originally had a cooldown that prevented us from spamming it. It costs half our energy pool every time we use it. Its damage is based on weapon damage, which means that daggers were sub-par for Fan attacks. All of this made it fairly ineffective – more of a gimmick.
Then patch 3.0.8 came along. The cooldown was removed so we just have to wait on a GCD. Daggers do 150% of weapon damage, so they are now very good with FoK. The only obstacle is that is takes half our energy for one use.
For any Assassination rogues that haven’t figured this out yet… the key is starting in stealth do take advantage of Overkill. I see a lot of rogues that don’t start a fight stealthed because of the slowed movement speed. If you want to use FoK effectively, you really need stealth. With that talent, your FoK costs only 40 energy for the first 6 seconds after you come out of stealth.
So… Assassination rogues… start in stealth… get your HfB stacked… get yourself in the middle of the tanked mobs… and…
FoK… now you are at 60 energy
wait on GCD, during which you regen 10 energy so you are now at 70 energy, and then…
FoK… now you’re at 30 energy
wait on GCD, during which you regen 10 energy so you are now at 40 energy, and then…
FoK… now you’re at 0 energy
wait on GCD, during which you regen 10 energy so you are now at 10 energy
Its been about 3 seconds since you came out of stealth. You don’t have enough energy for another FoK until you wait about 3 seconds, give or take a little latency delay and Focused Attacks procs. At this point you are still within the 6 second Overkill, so you’ll be able to hit one more FoK.
Therefore, if you start stealthed you can get off 4 Fan of Knives within 6 seconds. Trash still alive? You can Vanish and start again, although you’ll still need to wait for your energy to regenerate. If you are in a big enough group of trash mobs, that will keep you at the high end of the damage chart on any big AoE pull.
Its even easier for rogues that have Vigor for that 10 extra energy.
Using this, I have been right up there with the locks and mages on the trash pulls in Naxx where there are lots of little spiders and geists and such.
Note: for comparison, if you are not Assassination spec and don’t have Overkill, or if choose not to start in stealth, you can only get off 2 FoK before you have to wait on energy to regenerate for a full two seconds before you can throw a third FoK.
Note #2: This does not account for Combat Potency or Focused Attacks procs from your autoattacks while doing FoK