The purpose of leveling a class is not that you know it immediately, it's that you're learning it.

Learning these things for the first time is rather difficult, there is the novice training now; but that doesn't give you bonus enmity when you're in a dungeon and need to learn control, or if you have less gear than the rest of your dungeon members and they are ripping threat from you due to the changes that were made to reduce damage.

The reduced damage is affecting new tanks more than it's affecting people who are used to the control required for it.