At least in old word zones (Butcher, Steamfort and Ak'Anon) mobs seem to flee regardless if they have help or not. But I think it might be dependable on the level difference how soon a mob flees. Gray seem to run at 50%, blue seem to run between 20-40%. I'm not quite sure yet, I'll try to collect some data in the next days.

I think this is something that has changed over the years too.

I've been thinking about this, and again, I think undead mobs do not flee - it doesn't even make much sense; What is an undead? something that is already dead, but up and around again (living dead). An undead creature has no fear of dieing simply because it's already dead (has no need to flee for that matter).
On the other hand, a living creature will run, because he wants to keep living. Now, I haven't tested all the creatures on EqLive for this, but about 2 years ago, when I really played Eq Live, things like skeletons, did not flee when 'dieing' < I know, "But he's already dead!".
Fear is another subject , I'm referring to mobs that flee when they are loosing the fight. Skeletons can also be feared - so, the question is, dos the ncpspecialattks "flee" apply to fear ? if so, then we do need a new column for running while dieing of special code for undead.

I got typos in the above post and my edit time ran out; I meant we need code for the undead mobs that do not flee, or a new column in npctypes.

I believe you can just set "f" in special attack codes to disable fleeing on a per-mob-basis.

Yea, but will they still fear? I think flee was intended for fear?

Fear is "D" and "f" is fleeing. Since fleeing didn't actually work when this special attack code was put in, it was basically to have a setting that keeps NPCs from taking fleeing damage because they never actually start fleeing.

This will be in 1113.