While I agree with most points stated in this thread, nerfing amii monument is only a small part of what most people want to achieve. There are several cards which are at least not worse at skipping t4, these include batariel, frenetic assault and infect. And there are lots of other PvE-oriented cards that are simply too good for what they do like mutating frenzy.
I don't think there is a thing called balance when talking about PvE. There are two main outcomes of nerfing such cards. First of all, you change the rules of speedrun competition and second, you make it harder for those who don't give a damn about PvE but still need to farm gold and upgrades.
All in all, if you wanna change amii, you need to change all the hi-end PvE meta at once, remove the old records and let the scene breath anew. However, I don't think we are ready for those changes yet, as the game is still being explored and new records are set every month. But when it comes to bringing it back alive, then yes, that's the perfect option.