Drain Life

249per cast

Rank 6 · level 60 · before talents

Drain Life

300 Mana20 yd range

Instant

Transfers 51 health every 1 second from the target to the caster. Lasts 5 sec.

Talents that change it, each at full ranks:
 Soul Siphon · with 3 of your Affliction effects on the target  +89.7 Improved Drains  +49.8 Improved Shadow Bolt · after a Shadow Bolt crit  +49.8 Demonic Knowledge · with a demon  +29.3 Master Demonologist · with your Imp or with your Succubus  +24.9 Malediction  +12.5 Shadow Mastery  +12.5 Suppression  +7.8 Malevolence  +6.1 Pandemic  +4.3

All 6 ranks

Rank	Level	Per cast	Per second
Rank 1	14	49.1	9.8
Rank 2	22	68.5	13.7
Rank 3	30	108	21.5
Rank 4	38	137	27.4
Rank 5	46	191	38.1
Rank 6	54	249	49.8

Plan a Warlock build

Averages, counting crits and misses, with a typical weapon and no other gear or buffs, against a target your level. Talents at level 60. Worked out from the game's own data, the same way as the Foresight addon.