The best powerleveling method I've found so far is to do ragefire/deadmines until 20, then SM Cathedral until 40. I'm still trying to figure out the best place to go after 40. I'm using a 70 prot pallie as my power-leveling toon, which is working awesomely. You can do SM Cath in 2 pulls, getting about 4 runs / level for 4 of the toons. Since you have a mage, if you find a paladin friend to help you out you can do the insane paladin/mage trick described here http://www.edgeofnowhere.cc/viewtopic.php?t=391556. With that trick I helped level a friends rogue from 8 to 27 in 4 hours. We'll probably finish it out to 40 and have under 10 hours / played. After that it gets trickier to find a good instance, but I'm still looking around.