What they need to do in order to address in-party power-leveling is make it so that the higher the gap between you and the player, the lower EXP you get. If you are more than 8-10 levels lower than the highest member in the party, you should be getting little to no XP. This would prevent powerleveling, as well as it gives them the chance to make it so that we can try for higher rewards for our efforts. I would love to battle Kobolds, but Raptors are 10x easier for MORE experience than Kobolds were giving, even though the Kobolds were harder to kill.