Prius scary to drive in heavy rain!!!

I had some spooky freeway rain experiences. When it sensed slip it cut power, and the "surging" was disconcerting. I slowed until it went away, which was slower than just about every vehicle around me.

I assumed it was TC (the dash light was blinking on and off repeatedly), but later wondered if maybe VSC was at work (it was so noisy from the rain and wipers that I don't know if there was a sound/VSC or just the dash light/TC). If the traction was uneven between wheels, causing a slight random swerving, will VSC start braking wheels, trying to maintain the straightahead direction? That might add to the sensation.

I thought it was strange that I had to drive so slowly. Maybe the car is overconservative, but it meant I had to slow and change lanes (into the dangerous truck lanes). It was definitely an uncomfortable feeling.

Mild rain wasn't a problem, but this heavy rain was not fun.