Your Scorch spells have a 33/66/100% chance to cause your target to be vulnerable to Fire damage. This vulnerability increases the Fire damage dealt to your target by 3% and lasts 30 sec. Stacks up to 5 times.
Patch 4.0.1 (2010-10-12): Redesigned as a 2-rank, tier 3 talent (was a 3-rank, tier 4 talent). Improved Scorch now reduces the mana cost of your [Scorch] spell by 50/100%. Previous functionality folded into [Critical Mass].
Old: Increases your chance to critically hit with Scorch, Fireball and Frostfire Bolt by an additional 1/2/3% and your damaging Scorch spells have a 33/66/100% chance to cause your target to be vulnerable to spell damage, increasing spell critical strike chance against that target by 5% and lasts 30 sec.
Patch 3.3.0 (2009-12-08): The debuff from this talent no longer stacks, and instead can apply the full effect from a single cast of [Scorch].
Hotfix (2009-04-21):Shadow Mastery and Improved Scorch will no longer stack with each other.
Patch 3.1.0 (2009-04-14): Increased critical strike chance is now 1%, down from 2% per application of the Improved Scorch effect. In addition, the critical strike chance of [Scorch], [Fireball], and [Frostfire Bolt] is increased by 1/2/3%.
Patch 3.0.2 (2008-10-14): Now increases spell critical strike chance against the target by 2% instead of increasing Fire damage dealt to the target by 3%.
Patch 1.11.0 (2006-06-19): Now a 3 rank talent (down from 5 ranks). Increased to 3% Fire Damage taken per stack, for a total of 15% increased Fire damage. Duration of Improved Scorch increased to 30 seconds.
Patch 1.4.0 (2005-04-19): Redesigned. Scorch spells have a 20/40/60/80/100% chance to cause your target to be vulnerable to Fire damage. This vulnerability increases the Fire damage dealt to your target by 2% and can be stacked up to 5 times for a total of 10% increased Fire damage.
Previous effect: Burns the target for an additional 5% of your Scorch spell damage over 4 seconds. Stacks up to 5 times.