Warlock · Affliction · tier 2 · from level 15

Improved Drains

+82.1 Drain Soul

3/3 · level 60 · per cast · and 2 more

Improved Drains 123

Rank 3/3

Increases health drained or damage done by your Drain Life, Drain Soul, and Wrack spells by 20%.

Drain Soul +20.0% +82.1 Drain Life +20.0% +49.8 Wrack +20.0% +42.2

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.