S:L is/was way too powerful as a 1 point wonder that you get at the top of a skill tree. As it stands, it does several things: they attack and move slower, they are hit more often, and they take more damage. That is all for just one point at level 6. Functionally, it works more like a level 24 required skill like Decrepify.
The problem is that they can't really change the whole tree because one skill was placed in a very wrong bracket (or rather, they don't want to change the tree). So something had to change to keep it vaguely in line with not just other skills, but when you get access to it in the game. It was a fundamental mistake that they are band-aid fixing.
In my opinion, the correct fix would have been to change the tree and place Rancor at the top with its same lvl 12 requirement, have Death move to lvl 18 required, and slot Lethargy at level 24 with smaller nerfs to the effects overall.
It sucks most for non-warlocks because of charges, but they aren't going to do it the correct way and redo a bunch of their work on the UI/UX, especially on the backend.
I warned people the first day Warlock came out that this skill would get a nerf.