When talented correctly, it's possible for Rogues to have a 100% chance to apply Deadly Poison. This allows for more Envenom use, especially useful for PvE.
"Each strike has a 30% chance of poisoning the enemy" -Deadly Poison
"Increases the chance to apply Deadly Poison to your target by 10%" -Improved Poisons
"Following the Envenom attack you have an additional 15% chance to apply Deadly Poison " -Envenom
"increases the bonus chance to apply Deadly Poison when Envenom is used by an additional 45%". -Master Poisoner
Keep in mind, Precision increases chance to hit with poisons (not be resisted), not increasing the chance to apply poisons.