They reworked how Arcane Shot receives it's bonus's. This was changed in a patch long ago, but basically they nerfed the amount of +Magic Damage you could receive to your Aracane Shot. We used to be able to get 1k+ Crits with our Arcane Shot before the expansion came out, but we had to have heavy +Magic Gear. There's a few videos out there of Hunters at 60 soloing places like Scholo, BRD, etc.
With the way it works now, +RAP affects your Arcane Shot damage more then +Magic. And the ratio of +Magic damage to even = 1 more point of damage is just terrible.
Now with that said, +Magic Damage effects our Serpent Sting (nature damage over time) and it affects Volley. I've tested this myself, and I feel that with enough +Magic Damage, I can get my Serpent Sting and Volley to do quite a bit of damage. However the only problem is that you've just now traded your gear for +int/stam and +magic damage. The int and stamina might be nice, but you would receive no additional AP or Agility. Making your normal shots almost pointless.
However it does not affect your traps in anyway. Explosive Trap and Immolation Trap will do the same damage regardless of how much +Magic Damage you have.
Although on a side note it would be interesting to see a hunter with a 500 damage a tick Serpent Sting.