This may have been answered previously, but I thought I would address another issue involved with forming single-sphere tournament decks with the core game. Do heroes count toward the 50-card limit? I'm only asking because if one were to construct a single-sphere deck using only the core cards and adhering to the 3 of a kind card limit, the most possible cards you could have in the deck would be 48 if you don't count the heroes. I am including 3 Gandalf cards in the calculation as well. It seems odd to me that there aren't enough cards within the core set pool (refering not to the box but to the total available card types) to form a single-sphere tournament deck. This probably could have been fixed if they included another neutral card in the core, or even one extra card type for each of the spheres. I know this messes with the whole round number mentality of having a 30-card starter deck, but I would think the core deck pool should still have a card pool that allows single-sphere gameplay in tournaments. Granted, there will be expansions, and people can always make multi-sphere decks, but shouldn't the core card pool be capable of single-sphere play at tournament level, especially if they are going to impose a number limit on the deck? I hope I'm not coming off as complaining. I love the game, and I know that the game designers probably had a heck of time balancing everything and trying to figure out the right number of cards to produce. I plan on getting the expansions anyway. I was just wondering if the heroes counted toward the card limit given the limited amount of cards in the core pool.

I don't think that heros count towards the 50-card limit (on p. 5 in the rules booklet they say that hero cards don't belong to any deck). Strange thing that they only created 15+1 distinct deck cards per sphere in the core set, though. I got the game only a few days ago now and I really love it too, but didn't count the number of the cards until now ;-) But at least with Radagast or other cards in adventure packs, the 50 cards requirement can be overcome, as you already said.
Perhaps they expect a tournament player to obtain at least an adventure pack. After all, two additional core sets would be required for having duplicate versions of the cards which only occur one time in the core set (e.g. Grim Resolve).