Before the hotfix today, I had gone through Heroic USH a few times with no real deaths. When they used Mass Drain, it did a lot of damage, but was survivable. After the hotfix adjusting Theurgism and SDM scaling for Myst duration, Crypt Keepers are doing multiply times the damage they were before the hotfix.
An example combat message:
Crypt Keeper says 'Amven xux torak keptih!', pointing at Gnoth.
You just lost 1000 experience points.
[[10% Necro Resist]] Drugto loses 11637HP! Drugto dies. [[50% Necro Resist]] Gnoth loses 3056HP! Gnoth is hurt! [[15% Necro Resist]] Ryfon loses 5425HP! Ryfon dies. [[5% Necro Resist]] Ailuin loses 11010HP! Ailuin dies. [[15% Necro Resist]] Qildor loses 3383HP! Qildor is hurt badly! [[10% Necro Resist]] Ryul loses 4780HP! Ryul dies. Crypt Keeper gains 9822HP.