Hunting in the rain is a very personal decision. For me I hunt in the rain all the time. Heck I do 3 week long trips in different states hunting each year and of I didn't hunt in the rain I would miss half the days of those out of state hunts.
If you want to hunt in the rain and are only held back by worry of the blood trail you could get a string tracker from drifter bows and solve that problem.
As for feather protection all of the sprays, powders, covers, etc are all bandaids. To truly solve it and never worry about arrow flight in the rain test your broadheads and feathers in the rain. If you wet them and mat them flat with your hand and shoot them and they don't hit or fly the same as dry it's time to fix stuff. Tune the arrows to your bow, then start playing with feather sizes, broadhead, or add more forward weight. The more foc you have the less the feathers matter. I shoot 30℅ foc arrows and I also use a big Magnus 2 blade head and I don't even need feathers. See this video for that bareshaft broadhead shooting when I was first testing it.
http://tbwpodcast.com/video-37-efoc-bare-shaft-broadhead-test/ There is no right or wrong decision to hunting in the rain and there is a variety of ways to make it happen if you do.
But it is very important that if you do decide to hunt in the rain you make dang sure your arrows fly right and you can make an ethical shot and recovery.
You are asking the right questions and getting a great variety of good answers!