If I'm not strong enough to beat the enemy, it either kills me or I end up being unable to escape. So I just reset. I almost don't run in RPGs at all, unless the success rate is 100% (built into the system, smoke bomb-like item/ability, something like "Let Go" in the Suikoden series).
You can't run from any battles you'd actually need to run from, so no, I haven't. It also takes too long to restart the game due to the billions of logos and load time, so I just let everyone get oneshot.
When you make an assumption, you make an ass out of u and mption!
I run away whenever I don't feel like fighting. Right now I'm blasting through each area collecting the gathering points so fighting is a waste of time so I usually just flee if I can't 1-shot everything with Neptune's summon.
Some of the greatest catastrophe's ever committed by man have been done with the "Best of Intentions."