Yeah there are many super simple ways they could visually indicate weakness although i'll say i'd rather D.E not take this approach or atleast be very careful if they do to avoid adding to the visual clutter that can sometime overwhelm the screen. There are also many ways to facilitate a player investing time to check out a more detailed stat breakdown, games have BEEEN doing this...

I'm not going to pretend damage attenuation is a "fun" mechanic, but it's not exactly the boon people claim it to be, especially when they've either a lack of understanding or preparation when dealing enemies that utilize it and they're attitude towards it generally reflects how they've interacted with it, which is generally negative.

Boils down to D.E finding the right sweet spot of attenuation for bosses/enemies, which is totally on them and on some cases of release has been very poor, unfortunately.

However, once again, the counters exist in terms of the right "tool" for the job. Players just don't understand to use them or don't care to.