Well i think this topic is a bit mislleading in fact i think amii monument is only the tip of the mountain.....
The Problem when trying to balance Competetive pve eg speedruns and record hunting is obvious. There will always be 1 best strategy resulting in it beeing "op" compared to everything else. This does hit pve way harder than pvp since there is no "metagame" its jsut 1 best way = low variance.
Also i think there is a significant diffrence between something beeing overpowerd and something beeing "broken". For me i would consider stuff like lss or buffed up batariel "overpowered" since it does clear faster than prob every other strategy while there are still other ways to get the same result just way slower. I however would consider amii monument broken it opens up new tactics which are impossible to repicate in any other way.
however i feel like there are some more equaly broken mechanics for pve.
First of all there is the funneling strategy which saves insane amounts of time just by evolving 3 persons t1 energy into t4 energy with only the 4. person to actually spend power on monuments
enlightment is another candidate...
tbh almost all speedruns do abuse some if not all of those problematic mechanics not even mentioning various ways of void manipulation and i thik this is fine i dont think there is a actual way to balacne cards like amii monument either its op or useless. Im case it would get nerfed i guess the palyers would need some time to figure out if its still playable. If nnot screw it and the next card to nerf would be enlightment or decomposer or whatever.
From a non speedrunenr perspective i think the best way to break up the "boring" and "1 sided" pve meta would be monthly card restrictions or smtng. i would be intrested in the speedrunranking ladders if there was a monthly card restriction on lets say decomposer, shadow phoenix, sow, amii monument or some other crucial cards. I think this would actually require some new strats, creativety and would generate variance. Just starting to nerf card after card can not be the solution!