Deaggro

Egotistical mage (aren't they all?) intentionally frostbolts a spectator. While we watched, he ran to the doorway where they would emerge and died a quick death at their hands. Then they deaggro'd and went back upstairs.

Source: wiktionary

I found with lvl 66-67 mobs, I could get within 8 yards (the range where shoot turns red for being too close) without aggro. If a mob did aggro (and was a melee mob, not tried casters yet), just hopping high enough that I'm out of melee range causes it to deaggro.

Source: wiktionary

The druid works particularly well since you don't have to shift out of Flight Form to herb if you can low enough, so if I aggro something while picking the herb I just fly up until it deaggros, then fly back down when it walks off.

Source: wiktionary

If things are going bad, you can even run away and wait for the monster(s) to de-aggro.

Source: wiktionary