Actually, they boosted quest XP on the beta server to curb that a little bit. But you won't level up as before. Why? Because if you mentor down....you don't get the encounter bonus. This will make tearing up seb and Chelsith counter intuitive for anyone who isn't of that level already. You do get the same xp as soloing in a full group of six Player Characters though, so Skyshrine contested will be overcamped and the best xp available most likely.