http://www.mmo-champion.com/threads/...8#post18256428
"Finally, we were worried about mage mana regeneration at level 85. Arcane in particular works better when it has the advantage of the level 90 talents. Once Mists is released, Arcane will be able to perform fine while leveling up and running the occasional dungeon. However, we're in this rare "lame duck" period where players are still actively running what will very soon be lower level content (i.e. Dragon Soul and the 4.3 dungeons). As a temporary measure, we've doubled mage mana regen across the board to 2% per sec up until level 85. This bonus will start scaling down by 20% per level between 85 and 90. "
http://us.battle.net/wow/en/forum/to...36?page=13#259
It's already live, and they're buffing it more cause Arcane seems to still be really low compared to fire in DS. No it doesn't show in spell book. It won't be there at 90.