Killing Spree is a level 90 Outlaw rogue talent. It is an instant rogue ability that allows the rogue to deal a large amount of burst damage to an enemy (several enemies with [Blade Flurry] in their range).
Killing Spree works with [Blade Flurry], so popping both will make the rogue attack additional targets instead of focusing on the rogue's main target.
Killing Spree also deals incredible damage to single targets and quite often is more effective and reliable when other targets are not in range.
Since Killing Spree uses weapon damage, it deals more damage with slow weapons.
During Killing Spree, you continue to melee. Your melee swings will benefit from the 50% damage bonus provided by Killing Spree, and you should further enhance this by using [Slice and Dice].
[Adrenaline Rush]'s 20% increase to attack speed will also enhance your melee swings during Killing Spree, but since you cannot use abilities while Killing Spree is active, you will waste the potential DPS boost provided by the energy regeneration bonus during that time.
While Killing Spree is active, all enemies will de-target the rogue, practically rendering the rogue immune to direct damage abilities. Area of Effect attacks and existing Damage over Time debuffs will still damage the rogue.
Patch 7.0.3 (2016-07-19): Changed from a level 80 ability to a level 90 talent. No longer causes the rogue to be immune to roots and snares while active.
Hotfix (2015-06-30):Killing Spree no longer provides immunity to Crowd Control abilities, regardless of Battle Fatigue.
Hotfix (2015-06-29):Killing Spree should now correctly only provide immunity to roots, snares, and knockback effects.
Patch 6.2.0 (2015-06-23): Now only grants immunity to root and snare effects and the effect is now cancelled if the Rogue is affected by other crowd-control effects.
Patch 6.0.2 (2014-10-14): No longer increases all damage done for the duration. Its damage has been increased to compensate.
Hotfix (2013-09-18):Killing Spree's range is no longer being incorrectly modified by Blade Flurry.
Patch 5.4.0 (2013-09-10): Targeting has been changed. If [Blade Flurry] is not active, Killing Spree will now hit the Rogue's target 7 times or pick the closest eligible target if none had been selected. Killing Spree will continue to work as it has while Blade Flurry is active.
Patch 5.0.4 (2012-08-28): Attacks done increased from 5 to 7 and all damage done for the duration increased from 20% to 50%.
Hotfix (2011-12-02):Killing Spree should no longer return a script error when only stealthed targets are nearby.
Patch 3.2.0 (2009-08-04): Error message when no targets are in range has been changed to "Out of Range."
Patch 3.1.0 (2009-04-14): Now also increases all damage done by the rogue while active by 20%.
Patch 3.0.8 (2009-01-20): This ability no longer breaks stealth if it fails due to all targets being out of range.
Patch 3.0.3 (2008-11-04): Instead of making the rogue untargetable, now causes all players to lose targeting on the rogue and the rogue to be unstoppable during its duration.