You stop dragging the instant you hit the /corpse button. Unless you're suggesting there is some cool down IE they deaggro in 3 seconds without you hitting /corpse.
But that is wrong. As stated above, corpse dragging made you KoS until you left the zone.
http://www.project1999.com/forums/sh...t=73048&page=4
Covers it pretty well and it sounds like Nilbog got it right. But as I mentioned above, getting allied or non-KoS just to test the mechanic is a huge time investment. Can you create max-faction mobs that you can kill in NRo or Iceclad? To streamline testing on things that require max faction or any faction.