Warlock · Destruction · tier 2 · from level 15

Cataclysm

+26.3 Hellfire

3/3 · level 60 · per 100 mana · and 8 more

Cataclysm 123

Rank 3/3

Reduces the Mana cost of your Destruction spells by 10%.

Hellfire +11.1% +26.3 Soul Fire +11.1% +14.2 Immolate +11.1% +12.4 Conflagrate +11.1% +12.0 Shadowburn +11.1% +8.1 Rain of Fire +11.1% +8.1 Shadow Bolt +11.1% +7.7 Searing Pain +11.1% +7.5 Incinerate +11.1% +7.2

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.