It needs to be both imo. Also make an option where your highest corruption apply to all monos. spamming monos for weeks to get to a corruption that challenges your build is bad design. I almost always give up before empowered monos become hard or challenging content. Running the same easy content over and over and over and over again to get to your desired difficulty is just so bafflingly bad
I'm not saying that we won't ever do something like that, just that the thing that we've decided on in a design meeting was around stability.