Nerf Arrows of Harming

Arrows of Harming do too much damage, with one arrow of harming II being able to kill a player in one shot without enchantments. And since magic damage isn't blocked by armor, it can kill a player wearing diamond armor in two shots. 

They are also too cheap, incongruently with the rest of arrows. 8 arrows are tipped with a potion, but in exchange the duration of the potion is reduced to 1/8 of the duration. But since harming is instant, you get 8 arrows each doing the same damage as 1 potion. 

I suggest that the damage be nerfed, with harming I arrows doing 2 extra damage and harming II arrows doing 4 extra damage.