It's not really worth it since Nostalrius is incredibly populated. I just leveled a mage (currently lvl 56) and I never was alone at a spot for longer than 10 minutes. Especially the really good (and known) spots, like the Pirates in Tanaris or the Murlocs in Dustwallow (or the Orcs on Go'sheks farm in Arathi) are constantly farmed by multiple players.
http://db.vanillagaming.org/?talent#oZZMhMIcbIf you still wanna give it a try, I'd go with something like that. The extra range on blizzard and extra duration on chill effects are really important. Do not get Frostbite, as much as you want to. Its only a disadvantage for aoe leveling.