I think this game is in a great place in term of character balance and honestly @FelipeGames2000 has covered this more thoroughly and from an objective point of view. Essentially the original poster comes in and names three plant classes that he finds overpowered in some way and demands nerfs. He then proceeds to name I believe almost every zombie in the game 90% of which he thinks are under powered. He doesn't care to mention plants that are struggling or need help. Clearly the OP isn't objective and prefers zombies over plants. I would take what he says with a grain of salt.
The real problem with the game right now is Turf Takeover map balance.