JohnSnow
Hero
I wonder how much we glossed over the notion that henchmen were intended to be along as extra bags of hit points and melee attacks so that the adventuring day could last longer.Henchmen survived slightly less long than an unnamed marine in a xenomorph attack.
No matter how many characters set out, it very quickly became equal to the number of players.
Like the random soldiers who went with Perseus in "Clash of the Titans," nobody expected them to make it, they were just there to throw a few attacks and suck up damage. They were, quite literally, "tanks."
There's no (mechanical) difference between that and giving each PC twice as many hit points and a second attack. Unless that attack is a spell, of course.