"I guess you've never heard of +dmg scaling to cast time. For the +dmg you see, multiply that by the fraction of your spell's original cast time / 3.5 and that's how much damage you actually get."
Lightning Bolt and Frostbolt have the same original cast time (3 seconds), Frostbolt gets -5% +damage bonus for being a 2.5 second cast (brought back to +5% with Empowered Frostbolt), while Lightning Bolt gets the same +damage at 2 seconds as at 3 seconds. Even the +5% spell damage is more than equaled by Lightning Overload (A 5% chance to cast a second Lightning Bolt/Chain Lightning after any cast, and it will proc off itself and can crit). Both frost mages and Ele Shaman get 100% bonus to criticals. The +6% damage talent in Frost tree is matched by +5% damage in Shaman Elemental. Basically, with all the talents done and equal +damage/crit and no aggro issue (think Ragnaros style), Shaman will hit for the same amount of damage as a Frost Mage, but do it every 2 seconds instead of every 2.5.
However, mail +damage and crit itemization is piss poor, and as such you'll rarely see an Elemental Shaman with the gear to go toe-to-toe on the damage meter with a Frost Mage in equal quality gear (i.e. Both have Tier 4/5). Once you factor in AOE, Mages climb ahead easily. Arcane/Fire Mages will dominate a shammy day in and day out though, despite having only 50% (75% if more arcane then fire) bonus to spell crit. And even if the Shaman does manage to go toe-to-toe with a mage in a raid on the damage meters, he's going to pull aggro so fast that he's down in about 20 seconds due to the meager 10% passive aggro reduction that Elemental Shaman have. At least the mage can switch to better aggro reduction with Arcane Missiles or iceblock if aggro gets pulled
- JimmyOlsen: Level 70 Draenei Shaman, Uldum. 41/0/20
Lightning Bolt and Frostbolt have the same original cast time (3 seconds), Frostbolt gets -5% +damage bonus for being a 2.5 second cast (brought back to +5% with Empowered Frostbolt), while Lightning Bolt gets the same +damage at 2 seconds as at 3 seconds. Even the +5% spell damage is more than equaled by Lightning Overload (A 5% chance to cast a second Lightning Bolt/Chain Lightning after any cast, and it will proc off itself and can crit). Both frost mages and Ele Shaman get 100% bonus to criticals. The +6% damage talent in Frost tree is matched by +5% damage in Shaman Elemental. Basically, with all the talents done and equal +damage/crit and no aggro issue (think Ragnaros style), Shaman will hit for the same amount of damage as a Frost Mage, but do it every 2 seconds instead of every 2.5.
However, mail +damage and crit itemization is piss poor, and as such you'll rarely see an Elemental Shaman with the gear to go toe-to-toe on the damage meter with a Frost Mage in equal quality gear (i.e. Both have Tier 4/5). Once you factor in AOE, Mages climb ahead easily. Arcane/Fire Mages will dominate a shammy day in and day out though, despite having only 50% (75% if more arcane then fire) bonus to spell crit. And even if the Shaman does manage to go toe-to-toe with a mage in a raid on the damage meters, he's going to pull aggro so fast that he's down in about 20 seconds due to the meager 10% passive aggro reduction that Elemental Shaman have. At least the mage can switch to better aggro reduction with Arcane Missiles or iceblock if aggro gets pulled
- JimmyOlsen: Level 70 Draenei Shaman, Uldum. 41/0/20