I'm not the guy you responded to, but I think Kazakus is another card that isn't good for the competitiveness of the game. First of all, you don't know what mana cost your opponent picks. Sure, you can make inferences based on the matchup so that's the least egregious part. But then you have no idea which primary and secondary effect they pick, and the ones they are offered are random. You cannot possibly play around every potential combination, so the only option you realistically have is to play around none of them. In that sense, for the person playing against Kazakus, the card basically reads "Add a random undercosted spell to your hand." I've talked at length before about how Discover and Discover-like effects (ones that add cards to your hand from outside of your deck) are bad for competitive play because the opponent can no longer make informed decisions based on his knowledge of your deck and the matchup. Even if Ethereal Conjurer, for example, is less random than Babbling Book, playing against them is the same experience because you can't play around them. Kazakus is going to be a lot of fun to play with, no doubt, but losing to Kazakus is going to feel bad, the same way losing to Swashburglar or Babbling Book feels bad.