+1 to what crime dog said. More traction there in the wet than you'd think.
Wether driving or riding, the key is to be smooth with your inputs. Commuted on the 919 daily in the rain in Oregon with zero issues. In fact. Riding in foul weather/night is safer than broad daylight apparently. Motorcycle accidents involving other vehicles are much much lower compared to accidents that take place during broad daylight.
As to visibility, you get used to it if you train yourself. Meaning, don't have your wipers at full speed for just a sprinkle. For motorcycle helmets, there are things similar to rain-x that work really well.
For hydroplaning, it's all about the appropriate speed in response to the driving environment and whether tires are correctly treaded for wet conditions.