@stormanimagus my immediate response would be to say no. for these purposes I'm assuming that as a 2 mana spell it's a dead draw, especially given whatever sphere effects you will have. I think this spell will be at its best in decks that either:
- have the mana and need to cast additional copies as they draw them(I'm interested in it for legacy dark depths lists in this role, modern tron obviously, etc)
- will cast their first copy turn 1 and then end up not worrying about ever casting the rest(dredge or survival both might want this turn 1 and then have bazaars to discard excess copies to when 2 mana is too much)
in decks that don't fit one of these categories, I think this is comparable to mana acceleration in terms of being useful early game and dead later, but even moreso, as the dropoff starts as soon as you cast any other spell on turn 1; drawing a mox or a spirit guide on turn two or three still advances your gameplan, while drawing this usually doesn't.
mainly my questions are how often do you think you are going to be able to pay the mana cost for this, and how long do you expect your games to go? if you won't regularly have 1G+thalia then the card is essentially a leyline. I'm interested in seeing testing, and the ability of this to hit spirit guides is probably relevant for someone trying to maximize their ability to make big turn 1 plays.