Mark Rosewater, Magic head designer and weekly column writer, in many different occasions wrote about R&D will of creating the fewest number of cards that break the color pie. While I think this is a great decision, I don't understand what they are doing with blue creatures.
Blue has been since the beginning one of the strongest colors, providing card advantage, cantrips and counterspells; the drawback was having access to really bad creatures, most of which had a really high casting cost and some important drawbacks (I'm speaking of the days in which Serendib Efreet was banned for being too good).
In the last few years we have seen so many strong low casting cost blue creatures that have become format defining: Delver of Secrets is a staple in Legacy, is used in Vintage, Pauper and in few decks in Modern; despite some great graveyard hate card, Snapcaster Mage is widely used in Modern, Legacy and Vintage decks; with the print of Commander 2013 the CC3 slot has been filled with True-Name Nemesis, which has risen Esper and Patriot has some of the best decks in Legacy.
These awesome creatures in Legacy are used in decks that have access to the best cantrips ever printed (Brainstorm, Ponder, Preordain), the best counterspells available (Force of Will, Daze, Counterspell), one of the best plainswalkers (Jace, the Mind Sculpture): I think that the R&D team has pushed too far this color, making it way better than the others.
Why creating great blue creatures is considered acceptable and making a green counter, a white bolt, a black cantrip and a red mana accelerator considered breaking the color pie?!