What is moderate or even severe rain compared to light rain
Imagine flying into a waterfall for several seconds
If you hear the rat-a-tat-tat of hail on the nose dome or windshield you are already too far into it.
Agree that you probably can't thottle back any furthur than the FADEC will allow, but that is one of the fixes the manufacturers have put in.
As for aircraft speed, if you want it to be higher by all means do it with thrust, because high AC speed and low engine RPM are definitely the wrong way to go in this soup