(Note that rare here can mean either rare or mythic.) That means that you have a 23.4% chance of opening an additional rare in the two slots
Whirler Rogue feels like a card that might be really good right now
If you are not super comfortable with that just yet, you will want to identify what exactly your decks goal is before you begin building
The other two songs, Seldom All They Seem and One Last Hope, cost less to play, making it less of a drain if you decide to pay ink instead of having your characters sing them
Rather than pay mana for them, youll want to send them directly from your hand to the graveyard and then have them enter play via their abilities
In the right go-wide deck, such as Elves or Goblins, you can easily get boosts in the +4/+4 to +5+5 range going, too, which are very hard to deal with