RE: Who can use the most mana?
Yeah I kind of feel like the same, except it wasn't 14 months for me but only 6... still I love the game and play it almost every day. It's crazy how much the game evolved in the meantime and in what a good manner. The developer(s) do a decent job in managing the cards so the old ones don't become obsolete.
Here is a 99 mana battle I played (and won) but like you said, using 50 mana is quite a challenge, I don't think we will ever have cards to fill the 99 mana cap.