Haste Potion

Your calculation concerning how haste effects weapon speed is wrong. It's actually a common misconception that a 38% haste effect will make you swing/shoot 38% faster. On a 2.8 speed weapon, a 38% haste effect will make you attack at 2.03 which is a 27.5% faster weapon speed. The way WoW calculates weapon haste is it multiplies the attacks per minute by the haste percentage. This is so a 100% haste bonus won't cause a 0 second swing timer. >.> - 60 seconds / 2.8 weapon speed = 21.43 attacks per minute - 21.43 attacks per minute * 1.38 haste bonus = 29.57 attacks per minute - 60 seconds /

Haste effects are calculated multiplicative not additive.

Keep in mind that next patch you won't be able to stack potions like that. Most likely, this potion will count as an Offensive Elixir.