how long does it take you to die? What mobs do you bring back? The guards have a large reaction radius, however all NPCs are based on the 'tick' system right? That is, everything in the entire game that is automated runs on a 6 second rule. So, don't hold me to this, but IIRC every 6 seconds npc's do a 'check' in their reaction radious for KoS NPCs and PCs. If you happened to run in at the very begining of one of these cycles it could technically take them 5 or 6 seconds before reacting.
But then again, WR is not EQlive, who knows.