Now it's confirmed that there are spells that kind of block other spells I believe, but why would we use that if we can just tap the "left" button and evade the spell? There is no real reason, unless the spells have some kind of auto-targetting system, comparable to the one mass effect 2 had. For anyone who hasn't played me2, the engine noticed which enemy you were targetting and when you sent a biotic power at him, it would seek him out actively, following your enemy if he tried to get away.
Of course in Skyrim, the effect shouldn't be as strong as in me2, but I think it could really improve the magic system. There could be perks or skills to make that effect stronger for mages, and perks or skills that could lessen this effect when used against you.
This wouldn't make the game easier as enemies would have the same advantage. Also, it would force you to use your block spell correctly.
What do you think?