I'm assuming that they've gotten rid of the Block button (to block with Twohanded, you press button 2. To block with a shield, well, that's rather self-explanatory) and assigned that to dragon shouts.
Isn't it more logical that cast button is now used for dragon shouts and that that block button is used for right hand?
Also, I hope that I can decide in witch hand I will equip my dai katana since I wish to carry it in left hand (I'm ambidextrous, but I would still prefer to equip it to left hand instead of right) and use right hand button for blocking.