Burnout

Burnout is a Mage talent in the Fire tree. It increases the critical strike damage bonus on all Fire spells (similar to Spell Power) but incurs a mana penalty on every crit.

The fully talented 5/5 ability provides 50% and applies to the damage bonus or component derived from critical strikes. Since critical strikes hit for 150% of a normal strike, that critical bonus or component is 50%, half (50%) of which is 25%. Therefore, taking this talent makes your fire spells crit for 175% of their normal damage.