I realize this may be a bit late to throw my tiny bowler hat into the ring, but the original rule was better than the proposed change to 12 cards.
Honestly, a change to 12 favors elements with good rush deck options. If a team can build two of the exact same already established kickass rush decks, it's gonna end tragically for the others.
And as SG said, creating 5-6 decent decks with 6 per is totally feasible. Most elements can build two fractal decks and a flying weapon deck. They're not going to be great decks, but everyone faces the same limitations.
I'm also of the opinion that 240 cards ins't necessarily better than 180. Meh. I thought rules from the original post were just fine.