Tower of Frozen Shadow
 

Preface, I spent an insane amount of time in this dungeon in Velious. It was my favorite zone and every character I played on live ventured through this dungeon at some point in their lifetime.

First floor:
a shadowbone isn't fleeing at low health all the time. These used to run around 17 or 15% and they always ran. I killed roughly 100 of these and only 2 runners. Possibly only the lower leveled skeletons flee?

A little bit of era info from allah
http://everquest.allakhazam.com/db/npc.html?id=5636
One of the older comments from 2002 talks about a guy playing a necro down there and the shadowbones fleeing.

Reading an older post about lesser ice shades not dropping Globes of Fear, I got one of these while killing them.

Will try to update this as I get more time to goof around in there.

In all my days in Velious, I never messed around in the tower. I'll have to give it a shot. Thanks for the heads up.

This just dawned on me. The issue with the fleeing is I recall occurs most when the mobs sense the other mobs in the rooms near them. This causes them to flee more when the zone is clear but if its a full pop most won't run. Will have to test this but this would be why you are seeing inconsistency in what mobs run on low health.

Didn't play there during classic but I can definitely confirm they were rampantly running during 2003.