They are removing mastery from mages, and buffing icelance damage with like 50%, gonna be back to cataclysm days.
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Still rather have, a mage doing 2 icelances for me to die than playing vs a prot.
which means ice lance is getting buffed by 63%
Frostbolt - Also causes the target to take an additional 5% damage from your Frostbolt and Ice Lance, and your Water Elemental's Waterbolt, stacking up to 3 times.
Frostbolt no longer increases the damage of any spells. The damage for those spells have been increased instead.
Which means instead of the stacks, the damage is applied to the spell, your frostbolt, icelance, water elemental does 15% more damage, in additional the 48% ice lance buff. 15+48=63
You would multiply, not add you silly goose.
1.15*1.48=1.702, so it would be 70.2 percent.