Npc's need to run more if out classed as well as begging for there life. Beth's goal has always been to create a another world you can play in, make that world as believable as possible. This kind of things flow right into that.
Yeah, it really pissed me off at Kvatch when I took those band of soldiers in, and they
run at the Daedra first thing instead of running away or holding back so I can take care of them with my Finger of the Mountain. I've even had to invent an invisibility/shield/charm spell for when I'm taking my mage apprentice with me on missions so he/she doesn't get himself/herself killed. It's really unrealistic, and I hope it's something they change for Skyrim.
Well I dont see why human NPC's would know that they're out classed until they've been wounded, because I dont think skill levels exist in-game. And I don't think a bandit would run just because they had inferior armor or weapons.
Dude, I think even the most foolhardy of humans should know that when they come face-to-face with a Markynaz, it's kinda time to leave. Or find help from the Archmage.