I'm getting ready to enter my first Hearthstone tournament. This particular one is using a 3 deck format. But it seems a lot are going to a 4 hero - ban 1 format. What's the most common format especially if you get into the higher level tournaments? I'm considering crafting cards which I haven't done yet (have about 1450 dust at this point), and for this particular tournament at least it seems if I can craft class specific cards to make say a Handlock and a Zoolock deck or two different types of Mages like Secret Mage vs Frost Mage, it would be more efficient use of dust.
Do most hearthstone tournaments run a format that requires competitors to use multiple classes? Is this how Blizzcon and the other "majors" work?