What is the CHANSE to actually win something in the World of Warcraft TCG game?

Hi ive been hearing alot about the World of Warcraft TCG game... and im wondering if its actually worth trying to get anything, so what is the real chanse of actually getting a companion a mount or apperance change tool for ingame use? is it 0.01% or is it 50% or is it 1 to 10? (those was just examples i have NO idea at all...)