Someone PM'd me & said you do not see Narc if you do not clear the City... I never noticed that before lol
I started a petition on DE market for devs to display all positive and negative spells/buffs/nerfs on a city when you attack or defend but it was voted down.. maybe you try to do it here with better luck..
alternative way to know 100% it is active is to get your team to spam click narci at specific time, leaving 3 second gap between narci and cp is not a good idea when fighting a good team.
also keep in mind when wall is maxed out or has troy buff on top of it, it is probably much better to EQ it than cast narci because def % falls off significantly if you knock 1-3 levels of maxed out wall.
narci is usually good when clearing harbor and when wall is already in the lower levels.