They said they're gonna be releasing a bunch of new cards soon, so there will be more reason to shuffle. I actually don't mind the way it is now though. There's so much to get and it takes such a long time and progress is so slow that it's nice to have one thing complete at least lol.
Oh and faction XP will be useful for upcoming characters too, so it's good to haven't a bunch of that saved.
I think the purpose of rare cards is to encourage people to keep shuffling until they get them, but with the extremely high cost of locking a card no one wants to shuffle once they get a card they want. Not until they've saved enough gold for weapons and characters and other stuff anyway.