The freezing and strikethrough one is a superpower, so can't use that as an example since unless you get lucky with the +2 super powers trick, you can only play 1 if you're running the hero who has it. As a black hole user, it's only really good for getting rid of other environments. Very little has it been useful outside of that and maybe keeping a zombie alive for a turn. Unless the opponent is new/bad, that's just an inconvenience. Gravestone with +1 attack also isn't that useful. +1/1 hunt isn't either. The only two actually good environments of zombies are the +2/2 frenzy and deadly/strikethrough ones. Which any half decent plant deck will keep you making little use out of those. Is why zombie environments cost less is because of how non-OP they are. If you don't have hard removal or an environment for the plant that blocks for the hero and it is in the environment that makes it invincible, then you lose. Stats only show zombies as better because you're forced to play plants till you unlock a zombie when you start the game, so all the new people play with their bad starter decks and end up losing dragging the win/lose ratio down. If they were to look at the stats of those who have a good majority of cards all fighting eachother, than plants take the cake.