Borean Tundra, Amber Ledge - that's where I once again found my mage. It was time to get a few more XP bars filled and south west of Amber Ledge is just the place to be (for a level 70-72:ish mage at least). I first got there just to grind Rhino Meat for my warriors cooking, but found it to be a lovely place to gain XP at.
I went down to the awaiting packs of rhinos. They group in about five, so I run into the centre of a group, deliver a Arcane Explosion or two while running out and making a soft turn to group them tight together. If there is a Whooly Rhino Bull close enough they first get an Ice Lance in their butt as an incitement to join the party. When they are all in a tight group I serve them a Frost Nova and finish of with Blizzard for everyone. This gives 6-7k XP in almost less time than it takes to loot. After about 50 minutes of relaxed grinding, including selling of trash, some chatting, my dear mage was 350k XP (with rested bonus), 50+ gold and 124 Rhino Meat richer. If you are a skinner you'll earn even more.
Another great place for 70-72:ish are the mammoths south of the airstrip (around 58,31).