Don't forget that PCs have defenses against sneak attacks:
Barbarians: Cleave, Great cleave (Dead rogues don't sneak attack), Uncanny Dodge
Fighters: Disarm, Improved Trip, Cleave, Sunder, Whirlwind attack, etc.
Rogues: Uncanny Dodge, Sneak Attack
Wizards: Stoneskin, protection from normal...