I don't think this is necessary at all.
If the goal is to prevent people from sneak-attacking and then escaping, and returning, that could be solved by having health and armor of the enemies fully restored if all players have left combat. That's a much better fix.
I also don't really care much of other people ruin their own experience of the game by abusing sneak-escape to try to solo it. If they want to bore themselves out of their mind, it's not my problem.
