Ignite

From wow.incgamers.com

Talent: Ignite
Effect: Your critical strikes from Fire damage spells cause the target to burn for an additional % of your spell's damage over 4 sec.
Statistics: Rank 1 = 8%, Rank 2 = 16%, Rank 3 = 24%, Rank 4 = 32%, Rank 5 = 40%.