We're getting our first significant rain in about two months today in N. VA. I noticed the same thing with the 300D. Requires more pedal pressure to get it to stop the same way. At first I thought the vacuum boost was failing. It's not pulling to one side or anything, just noticably less effective.
I would describe mine as "worse performance" but not "scary". It seemed to get a little better as the trip went along. It still stops well with plenty of pedal pressure, as I did have to stop suddenly for a red light.