Damage tax The damage tax refers to an old side - effect of the Improved Fireball and Improved Frostbolt talents for the mage class . The damage tax lowered the amount of spell damage that effected Fireball and Frostbolt by 2 % per point in the respective talents . The damage tax was introduced in patch 2 . 0 . 6 and removed in patch 2 . 3 . Each of these talents reduces the casting time of the associated spell by 0 . 1 second per point . This effectively increased the damage per second of those spells , making them must - have talents , as Fireball and Frostbolt are primary damage spells ( depending on talent build ) . Blizzard developers may have felt that mages were doing too much damage compared to other classes , thus the damage tax was introduced to lower overall damage output . With the damage tax , the Improved Fireball and Improved Frostbolt talents still increased damage per second , but not by nearly as much as without it . As another side effect , the damage tax lowered damage per mana or Fireball and Frostbolt , making the talent a tradeoff between damage output and efficiency . For example , each talented Fireball would deal less damage than an untalented Fireball , but more could be cast over a period of time , yet the mana cost remained unchanged . Formulas . Frostbolt ' s spell damage coefficient is normally 81 . 4 % of total Frost spell damage , while Fireball ' s spell damage coefficient is normally 100 % of total Fire spell damage . The spell damage penalty from the damage tax is multiplicative , and is applied after the additive spell damage bonus of " Empowered " talents , Empowered Fireball and 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 : The following formula will compute the spell damage coefficient for Fireball with points in both talents , where X is the number of points in Improved Fireball and Y is the number of points in Empowered Fireball : Note that the cast time reduction does not affect the base damage coefficients , Fireball it is still based on a cast time of 3 . 5 seconds and Frostbolt is still based on a cast time of 3 . 0 seconds . Using Improved Fireball as an example , and ignoring Empowered Fireball for now , taking into account only spell damage , the following equation computes the DPS of Fireball . In this equation , d is the amount of Fire spell damage , B is the base Fireball damage , and X is the number of points in Improved Fireball . Solving this equation for zero points and five points in the talent gives : These two examples illustrate that before talents , each point of spell damage adds 0 . 2857 DPS to Fireball , while after talents each point adds 0 . 3000 DPS , meaning that Improved Fireball with the damage tax is an overall DPS improvement regardless of the spell damage penalty . The same calculation for Improved Frostbolt shows the same result : With the damage tax removed , the equation for Fireball DPS becomes : A mage gains 0 . 3333 DPS per point of fire spell damage , compared to only 0 . 3000 DPS with the damage tax in place . For Frostbolt without the damage tax : A mage gains 0 . 3257 DPS per point of frost spell damage , compared to only 0 . 2931 DPS with the damage tax in place . In conclusion , the damage tax lowered DPS but never lowered it compared to not taking the " Improved " talents at all .