There was a hotfix to classic wow that happened fairly shortly after its release that affected the way mobs leashed (specifically in packs together.) You used to be able to split apart mobs that leashed together so that some would reset, and the one you were shooting would not. this was changed about a month or so into classic wow.
Making a major edit:
I’m looking for the hotfix note and date, but they don’t go back that far surprisingly. Does someone know where I can find this information? I found the date here after a significant amount of Googleing: WoW Classic Hotfixes -- Updated November 16
The hotfix reads:
October 22, 2019
WoW Classic
- Fixed a bug that caused creatures such as Solenor the Slayer to misbehave when pursuing the player. Groups of creatures that commit to combat as a group will now all continue to pursue whenever any one of them are struck by a player attack or ability.
So leash behavior, for as long as I can remember, did not have packs of mobs that leashed together. I.E. one could pull a pack of mobs (in the open world not in a 5 man dungeon) and continually shoot or hit it to ensure that it did not reset, meanwhile other mobs that were part of that pack would reset due to not being hit.
So I guess my question is really twofold: Did OG vanilla wow ever have the current leash behavior seen in classic and classic wrath? I don’t remember it, but that doesn’t necessarily mean that it wasn’t ever there. If it did, when did it change to the interaction that I do remember, where you can essentially split up packs of mobs by only hitting one, and ignoring the rest? It does have this behavior in retail wow, so it does absolutely change at some point.