There are many combos you can use with an instant "make any spell have flashback" card. The 2/1 weenie part is just icing on the cake. Some of the older discard spells like Brain Freeze would be crazy powerful to give an example. For 6 mana (going off the idea of saying it should four instead of two), you can instantly make your opponent lose 9 cards+3 for whatever he played that turn. That ain't too shabby considering you only had one card in your hand and a card you probably already used to begin with.
Speaking of balance, you should take a glance at some of the interviews with the lead designer of MtG. The guy pretty much tells you Power Boosting is a myth and the game isn't isn't being watered down with overpowered cards. Meanwhile, he admits they don't care about what the older sets have in their arsenal and how it could have an impact on the players who don't play in tourneys. They treat the "product" one block at a time and can't be concerned with how their older product could mesh with the new sets.
