Found this:
http://www.eqmac.com/forums/viewtopic.php?t=6606
"Some NPCs, such as the Kobold Shamans in Nagafen's Lair, cast See Invisible on themselves and their allies; and this will make "sneaking down" into such areas more difficult and sometimes impossible."
This as opposed to what it is now, with mobs spawning with see invis.