Warlock · Demonology · tier 4 · from level 25
Decimation
+15.7 Shadow Bolt
2/2 · level 60 · per cast · below 35% health · and 1 more
Decimation
Rank 2/2
Reduces the cooldown of your Soul Fire spell by 90%. When you cast Shadow Bolt or Searing Pain on an enemy below 35% health, they deal 6% increased damage, and for the next 10 sec your Soul Fire spell has its cast time reduced by 40% and costs no Soul Shards.
Averages, counting crits and misses, for a level 60 Warlock with a typical weapon and no other gear or buffs, against a target your level. Worked out from the game's own data, the same way as the Foresight addon.