What I think is that there should be too types of exp rewarded from quests. One is the normal kind for your wizard, and another for your pet. Your pet should get about 5% of the exp you get. Like for a quest that gives you, say, 50 exp, your pet should get 2 or 3 exp. For the ds quests if you get 1500 your pet gets 75. Anyway that is just my idea. Oh and your pet doesn't get any exp if you get below 20.
I do agree that pets should be leveled up quicker but not by running around your dorm or castle. If this did happen then having an Epic or Ancient pet may seem less speicial. Example: One wizard justs spent hours leveling up their Ninja Pig pet by playing minigames and batteling enemies to earn pet snacks and now it is at epic then the wizard goes to show his friends. When he gets there he notices that one of his friends also has an epic Ninja Pig but he only got it a week ago and he hasn't played for days. His friend tells him that he didn't play any minigames to get it to epic, he just let it loose in his castle to play with his piggle. Then the wizard feels sad and his Ninja Pig doesn't feel very special any more. He then sells his Ninja Pig and uses the money to buy something else. While his friend is raising pets by the dozens by letting them loose in his castle.