Kunark mobs gave up pursuit in classic and re-engaged if you came back into range.
 

When kunark was released on live I remember one thing that stood out to me as very cool and it was that if you ran far enough from a mob in outdoors zones of kunark they would stop pursuing you. if you came back range of that monster it would (somehow know where u were and) re-engage.

Am I remembering this correctly?

Definitely remember them dropping pursuit if you ran far enough. Not as sure about the re-engagement once you came back though.

I do remember them re-engaging if you came back in range. I thought that's how it worked on this server too though; I could be wrong.

No, they just follow you to zone. They don't tether.

This used to be implemented here but they had to remove it, I think because it was so horribly buggy. And also it just isn't a very fun mechanic. They also weren't 100% sure how it worked and there were conflicting reports from different players about it.

There was trouble with this coding for quite some time durring my internship for SOE pre-velious. It was refrered to jokingly as the rules for disengagement (sp?) it was met under the following conditions:

1.) if target= >25% HP and distance = not visible (outside of the max clip plane of a player) then /disengage (retain aggro list)
2.) if target - >25% HP and distance from spawn = > not visible from pathing then /disengage (retain aggro list)
3.) if mob <50% and Player >50% and distance between mob and player increasing at not visible from pathing for more then 60 seconds then /disengage (retain aggro list)
^
basically if the player is running while the mob is below 1/2 life then they would only chase you for 60 seconds. (never understood this one and i believe they edited it out due to problems with kiting.)