Avman,
I think you're oversimplifying, especially on big jets. We expect one serious injury per evac and one fatality per two evacs. That means there's a 50% chance that when you initiate an evac you'll cause a fatality. Yes, in a Manchester scenario throw them out the side asap. However if the fire indications cease after the fire eng checklist then it's definitely worth thinking twice.
Just my two pennies worth.
LD