Improved Scorch

From wow.incgamers.com

Talent: Improved Scorch
Effect: Your Scorch spells have a % 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.
Statistics: Rank 1 = 33%, Rank 2 = 66%, Rank 3 = +100%.