Never saw that. but i figure it would be something to handle in house rules. I figure it would be an auto rout from a rules perspective. But ya you start lossing then take the rout your self. you don't want all your heroes OOA any way and keep fighting as you then have no exploration dice any way. unless your goal is to also make them get the same thing but then your still taking a higher chance of larger losses then your enemy.
I feel your pain with heroes going OOA and then dead. I have a few warbands that happens to and it makes me mad to no end! every one else advances and you grow stagnent for need to replace those dead.