One small thing that should be fixed asap:
If one surrenders the game, the win for the deck and thumbs up/down should not count. (And I don't mean when searching for a specific deck as was discussed here already, but when actually playing a random deck.) The problem is that, due to the rather low amount of decks, I fought against certain decks 2 or 3 times already. It's not representative if that counts as 3 wins and 3 thumbs up (or down).
On another note, the level system still is confusing and I would ask anyone rating decks not to include that into their rating. Imo, if a well built mono Life is level 30, then an unupped single mark single draw 20 HP deck can't be >level 10, but I see that quite alot.