Do you really think sword and shield will be viable?
Even with max block, I know so many people who fail at things like Paladins in d2, they had very lil survivability, most of the times, they'd get one shot or 2 shot, regardless of their block level.
We're talking about D3. How block works in D2 have nothing to do with D3.
Will Sword/Shield barbs be viable ? It's impossible to know. But the barbarian has a shield mastery skill, so they have intention to put shield as a viable option for the barbarian.