So, I'm really worried about this whole "few higher rarity" thing. Lots of games say that the higher rarities won't be tournament staples (see everything WotC said about Mythic rare when it introduced it). It always turns out to be false.
Well, we can assure you that the higher rarity cards in the core set and first expansion are _not_ something you'll need to be competitive in the game. It's a little too early to reveal specifics, but I can say that the extremely stupid rarity levels do not give a player an advantage.