Apparently, cinder drops in helltide are down drastically right now, too, but it might be a bug. So, not only do you need more of them to open the mystery chests, but you're getting less of them overall. I think their ultimate goal might legit be for you to be able to open just one chest per helltide. The days of being able to make a run with two mysteries and maybe a couple of armor chests are DONE.
True, but these changes don't really achieve much. The strongest builds are looking like they're still going to be the strongest builds, but everyone just outputs less damage, takes more damage, and gets less XP and less rewards in return.
I'm guessing that a lot of these nerfs are built around advantages that are coming with malignant hearts, but that only helps people playing on the seasonal realm, and will be back to just being flat nerfs when the season ends anyway. And even then, considering that overall incoming damage will be worse, having to give up the extra armor you'd normally get from jewelry sockets to use hearts, it's still not looking great right now.