Mage · Frost · tier 2 · from level 15

Improved Frost Nova

Rank 2/2

Reduces the cooldown of your Frost Nova spell by 4 sec.

Doesn't change the damage or healing of any Mage spell.

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