Improved Frostbolt

Improved Frostbolt
Improved Frostbolt (5 ranks) Reduces the casting time of your [Frostbolt] spell by 0.1n sec.
Requirements
Class	Mage
Properties
Affects	[Frostbolt]

Improved Frostbolt is a mage talent that reduces casting time of the [Frostbolt] spell by 0.1 seconds per rank, up to 0.5 seconds at rank 5. As a side effect, this talent also decreases the spell damage coefficient for Frostbolt by 2% per rank, though this is not listed on the talent description. This talent significantly increases the DPS of Frostbolt, making it a key talent in Frost specs that rely on it as a primary damage spell. The spell damage coefficient penalty reduces damage per cast for higher level mages that have a lot of spell damage gear. Despite the penalty, the talent always increases damage per second regardless of how much spell damage the mage has.

Rank	Cast Time	Spell Damage Penalty
1	- 0.1 sec	- 2%
2	- 0.2 sec	- 4%
3	- 0.3 sec	- 6%
4	- 0.4 sec	- 8%
5	- 0.5 sec	- 10%

Notes

[Frostbolt]'s spell damage coefficient is normally 81.4% of total Frost spell damage. The spell damage penalty from this talent is multiplicative, but is applied before the additive spell damage bonus of [Empowered Frostbolt]. With 5 points in Improved Frostbolt, the coefficient is (81.4% * 90%), or 73.3%. The following formula will compute the spell damage coefficient for Frostbolt with points in both talents, where X is the number of points in Improved Frostbolt and Y is the number of points in Empowered frostbolt:

(.95(3/3.5)(1 - .02X) + 0.2Y

Note that the cast time reduction does not affect the base 81.4% damage coefficient, it is still based on a cast time of 3.0 seconds. Taking into account only spell damage, cast time and points in Improved Frostbolt, the following equation computes the DPS of Frostbolt. In this equation, d is the amount of Frost spell damage, B is the base Frostbolt damage, and X is the number of points in Improved Frostbolt.

(.95(3.0/3.5)(1.0-0.02X)*d + B)/(3.0 - 0.1*X)

Solving this equation for zero points and five points in the talent gives:

0.2714*d + (B/3.0)  @ 0/5 Imp. Frostbolt
0.2931*d + (B/2.5)  @ 5/5 Imp. Frostbolt

These two examples illustrate that before talents, each point of spell damage adds 0.2714 DPS to Frostbolt, while after talents each point adds 0.2931 DPS, meaning that Improved Frostbolt is an overall DPS improvement regardless of the spell damage penalty. For more details on Frostbolt damage equations, see the main [Frostbolt] article.

Past changes

As of Patch 2.0.6 each rank of "Improved Frostbolt" now reduces Frostbolt's spell damage coefficient by 2%. Prior to this patch, the talent only reduced cast time.