Nerfing them would keep the deck alive, but not overbearing, so it wont be nearly as popular but will still exist. Ergo you have another of many vallid decks, and thus more diversity. Removing it, just means one less deck, and thus less diversity.
Magmar has a very balanced base, UP added several new decks that see a lot of play, it increased diversity, without power creeping the faction. A PERFECT example of how to make expansions that keep the game fresh, increase diversity, without powercreep or rotation.
MTG opting not to, and being paper, prevents balance patches from being really feasible, yet a simple ban list on eternal formats has proven that even with a massive pool eternal formats can be both successful and fresh.
Forcing players to do anything is not good. Give them the option. More options means diversity and fun. Less options just means less diveresity. Yea balance patches need to happen, and they are more important then new content, they should be the primary focus of the devs.