You can exile a card each turn, and never have to sacrifice your graveyard hate piece if you're not ready to
The Prerelease is your first chance to play with the new cardswhich means you'll have a leg up on the competition and be able to experience Oath of the Gatewatch before anybody else
It frees up space and gives you extra cash for things youll actually use
Whites weaknesses are card draw and ramp , which is why strong white decks usually lean heavily on synergy
You won't find value in it every game, especially if you're effectively controlling the board with all of your direct damage tools, but if you find it at just the right time you can gain a two, three, or even four lore instantly, which is often enough to close out a match in a deck like this
Five mana to remove three different targets at once is already strong