What i did was make a mage on the main account then a rogue on the recruited account. But my friend has a 70 Demo lock. All you do is go to an instance at the appropriate lvl with the lock in your group. You make a macro that does
/kick (locksname)
/invite (locksname)
Then you tag as many mobs as you can with fireball or whatever, once tagged have the lock send the felguard to kill them. DO NOT DO ANY DAME ON THE LOCK THOUGH OR THEY WONT GET FULL 3X EXP.
Shot version:
So basically only the pet is killing when the lock is outside the group and all the tagged mobs by the low lvls is full exp i was doing up to 3-4 lvls a run like this