Interactions are easier -- you have to use the names enough to make sure the reader knows who is who. Well, somewhat easier, especially if they are not the same sex (or one of them, but only one, is an "it'), and there are only two of them. I have stared at passages where two characters are interacting, and the passage seems positively overloaded with proper names, but what can you do? Things have to be attributed to Jill or Selysette -- especially if you are writing omnisciently and the very thoughts could be either.
It's when a character is, say, picking his way through a labyrinth alone, or casting a spell, or what have you, where other characters are relegated to off-stage or brief references to assure the readers that they did not fall off the face of the earth. When "she" is always and obviously Selysette, why are you even bringing it up?
My own impression is that to use more pronouns and fewer proper nouns gets the POV tighter, and more proper nouns does the reverse, but that may just be the characters who do it.
