This happens ALL the time.
Some noob barb/hunter jumps out, totally gets the drop on me, so I just heal and start attacking back. Then they just RUN AWAY! As soon as they're losing the battle.
If you pick the fights, you can bloody finish them! As a mage I can't catch anyone up, as a conjurer I can do hardly any damage, if i attack YOU it's fair enough to run but if you attack ME, and then run away, then what was the point in even attacking in the first place?