I think something along the lines of how the Paladin Detect Evil used to work would be cool as an AoE effect, but it does not work towards the true intent of this spell. If Dulan was in Hlint and someone used the spell with Key, Remiel, Ozymandias, Acacea, Dervish, and Renji around you would get..
"There is an ally of Toran near. There are four enemies of Toran near. There is one whom does not have a divine connection near."
No names would be given, and everyone's faith would be kept to themselves generally. However, this spell -needs- to stay the way it is because of the fact that Clerics shouldn't be punished for raising someone whom they had no IN CHARACTER way of knowing who their God is. Even as an AoE, it still wouldn't serve it's purpose. Orth explained this a few times I think.
The visual effect or not, if you do not want to be seen casting it, just use an invisibility spell.