Scrap the current Lvl 90 talents and increase our base damage by X% to compensate.
Replace the current talents with similar ideas to the following:
Ice Shield (or Dalaran Dome as mentioned earlier): 2 or 3min cd. Reduces damage taken by x% over X seconds while players remain in the "dome"
Mana Portal: Mage casts a portal to the Nether, allowing loose mana to seep through and be absorbed by fellow party/raid members. (have it function similarly to mana tide and/or lightwell)
Wild Fire: (similar to a warrior's crit banner) Nearby party/raid members receive x% extra crit rating for X seconds. (Include some kind of flame graphic on each affected raid member)
These are mostly just brainstorms and I'm sure they could be improved upon.