Some evidence already reported here on flee distance from you.
https://www.project1999.com/forums/s...d.php?t=304581
Also, leash is Classic in all zones. Torven did some current live testing of distances and they vary by zone, and sometimes within zones. Who knows if tweaked over the ages.
Here is a dated dev response on leashing:
https://web.archive.org/web/20010822...ve/arc77.shtml
Gordon on Kunark
[Quote from original post: 2) In Norrath proper these mobs will chase you all the way to zone to kill you because they are mad at you.]
No, they don't. All over, NPCs will not pursue you if you are out of a certain range. Try rooting a fire beetle on the Northeast side of east commons, then run with SoW to the Nro Tunnel. If you get far enough away before the root breaks, it won't pursue.
The zones being bigger in Kunark do probably exacerbate the problem, since the zones are bigger, and someone is more likely to be able to run a good distance without hitting a zone border.