The goal isn't to be faceroll easy like LFR. Even making LFR 15% harder probably isn't enough.
If I take the example of a friends and family guild I know, they started progressing at a decent pace in T14 once T15 came out with the T14 10% nerfs. And they are still pretty terrible, but at least they can get a real sense of accomplishment when clearing a new boss because it is still hard enough to be a challenge. 10% down from Normal is all that is needed, with the same mechanics as Normal.