Has never seemed to unbalance anything in my games. Just something with a magical vibe for those characters to do or contribute in a small way to otherwise combat scenarios favoring the more militant classes. In my mind, I think of Tolkien Hobbit scene with Gandalf and the crew in the trees getting assaulted by goblins and wolves (worgs). He throws volleys of little fireballs here and there... nothing massive like a true fireball spell, but lighting fur on fire and causing a little damage.
Using my own rules, this would mean that Gandalf was over fifth level, eh? So he chose "fire" variant.