The barbarian has ground stomp with a 3 second stun. The monk has a 5 second blind from blinding flash. The witch doctor has a 5 second fear from horrify. The wizard has a 3 second freeze from frost nova. The demon hunter has a few skills that slow movement speed for a few seconds. Will these affect bosses? Or will bosses be immune to these modifiers? Has anyone tried these on the skeleton king?
Moreover, Leoric is not even an Act Boss. I believe that Act bosses would not be affected by any type of CC and snares would have extremely reduced effects on them.
I hope they manage to work in SOME kind of effect from using these skills even if "freeze" becomes "slow" and "blind" becomes "blurry" with corresponding reductions in penalties but not elimination. Most of the passives and runed combos have debilitating effects - it would be a shame if most skills became useless against bosses and the whole fight became a "do enough damage before they kill you" basic DPS fest with no strategy.
Of course since boss runs will basically be a less than optimal way to get gear most of us wont care - until/unless we cant progress the game with our build.