Well, I spoke too soon on ALB earlier. Seems there's a bug in casting. I just tried it again and here's what I found. A friend and I went into rats to test it.
CAST -- affected everything in the room, including my friend. I.e. it acted like CAST AREA.
CAST AREA -- affected everything in the room, but not my friend. I.e. it acted like CAST CREATURES.
CAST CREATURES -- affected only the rat I was facing. I.e. it acted like CAST.
Whee!
-- Player of Eyuve