Well i dunno if this have been posted but some guy posted that you can with flumper bla bla.. well this trick is abit better..
Simply go to Blasted lands (Going through Dark portal)
Run up the hill and you will see Servant of Razelikh
These mobs are binded to a quest where you need to destroy some stones or something, but when you don't have the quest you can't destroy the stone and then the mobs get invulnerable and you get still hit them.
The whole point is - They do low damage, they can't die, you can't die (well its hard), you gain weapon skill, you win.
As a resto shammie you can go afk (if you have Nature's Guardian talent) and you will automatic skill up your weapon skillz
But any class can fight these for long time since they are low lvl. You can also test your dps on these if you like (a friend of mine uses this to test dps).