As a casual player, I find it hard to give a opinion about high end game. I think it is really hard to debate about balancing issues because my decks seems so powerful at lower ranks but after raising some ranks I get trashed by decks of the 4 factions. I think it is really hard to make a 100% balanced game, I am actually positive surprised by the current state of the game.
I think the devs should take a look at the strategy + faction + kind of decks played by the majority of people at high end ranks. If all high end ranks only play 1 or 2 factions I think we have a problem. If all 4 factions are played by the 100 and 200 high end ranks at similar proportion then I think it is okay.
I think the devs should select some possibile OP decks (with different strategies, with weather, breed, gold digger and so on) from each faction and test against each other with several plays. If the winning rate after 200 games are similiar for each faction then the game is balanced.