Thorn of Amethyst has been used in elves sideboard, so Thalia wouldn't be unusual if one would splash white.
The problem with such cards isn't their hinderance to us. Paying one more for Glimpse can slow us down a turn for comboing, but that is about it. The problem with such cards are their lack of usefulness. It doesn't seem to help against storm combo enough. Comes out too late and is pretty easy to disrupt. And against control decks it doesn't feel like it does enough to slow them down.

