Rogue · Subtlety · tier 6 · from level 35 · needs 2 points in Dirty Deeds

Quietus

+16.1 Ghostly Strike

5/5 · level 60 · per cast · below 35% health · and 2 more

Quietus 12345

Rank 5/5

Your Sinister Strike, Ghostly Strike, and Hemorrhage abilities cause 10% more damage against targets below 35% health.

Ghostly Strike +16.1 Sinister Strike +15.1 Hemorrhage +12.7

Averages, counting crits and misses, for a level 60 Rogue 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.