The level 90 Mage talents — Invocation, Rune of Power, and Incanter's Ward — were controversial in beta, and they continue to be controversial in the Mage forum now that people are hitting level 90 in the live game.
For a bit of history, the level 90 talents were introduced in the second major version of the Mage Mists of Pandoria talent grid. The Polymorph tier had been widely panned when the original grid was introduced, and many Mages had also made clear that we preferred to have thematic options available; many Frost Mages wanted Frost talents, many Fire Mages wanted Fire talents, etc. However, there was also general agreement that certain Arcane utility spells felt sufficiently universal that they didn't present a thematic problem for any spec. Polymorph was one such spell, but very few people liked those talents. A tier of talents modifying Evocation was a popular suggestion, and Blizzard ran with that idea.