Check out the PVP section aswell.

In general, I think you'll get owned properly, especially as fire. Since you're very very very squishy. As single player you can still blink and run all over the place, which is a lot harder for a multiboxer. This very basic reason is why imo, mages can't be boxed as succesfull as say an elemental shaman, who are much sturdy and can heal.

Besides the whole boxing story, I think Frost mages are -awesome- for RBG. You'd have 6 rings of frost and what not.

Good luck anyhow