Why shouldn't arrows have different DPS? Not all arrow tips are the same, nor do they do the same thing.
This is a very good point. Whats interesting is that the archer started as a class that by purchasing different arrows you would be able to do different kinds of damage (originally the build was monsters were weak to different kinds of mele attacks i.e. slashing piercing so on and so forth) but when Yoshi-P took over (not that I am complaining he is doing awesome) the mele damage types went out the window. I would like to see them come back just so I can justify paying 20k+ a stack for arrows. I would craft them but I find crafting tedious and annoying.