Hi,
As for water entry from rain into the fuel tank. That is now an issue of the past. It was corrected with additional frame drain holes somewhere around the 17/18 YM's.
HOWEVER.
I recommend that if you have any plans to be in a mud hole or even cross a creek floorboard deep you vent the fuel tank. Too many issues where people "never planed" to be seat deep are left stranded with a fuel tank full of water because it sucked it in. I would really only recommend the fuel tank and sub trans at very least since they are both right there under the seat. The other vents are not considered critical.
Here is a post I made long ago showing why fuel tanks get full of water so fast.
Multi - PSA - Fuel tank breather hose - IMPORTANT modification for ALL!