Placed in a combo with a modified Killing Spree, it is possible to triple the shadow warrior's attack value.
Note that, like all CA's in the Death Warrior aspect, casting speed is determined by weapon speed, and can be boosted by weapon lore skills and +% attack speed. Likewise, the casting speed will be penalized by wielding a weapon with too high a level.
Pros and Cons
Even with no mods, attack value is increased considerably
With the 3b (Leader) mod, this becomes a very effective tool in Multiplayer
No way to reduce cooldown time, only increase duration