Following up on the Castelli Assos rain shells pictured above, we had high 30's pouring rain all day yesterday and my hands stayed almost completely dry after an hour. The main issue is perspiration, you will be in trouble if you have too much glove on. That is why I like how I can vary what gloves I wear these shells over. The price is a total rip-off though, I would just get XXL dish gloves. There is in fact an online bikebpacking place selling XXL dish gloves just for this purpose which I ran into at some point.. five bucks a pair.
For colder temps I recently decided to get some
heated lobster gloves. I ski in very cold weather so they will be mainly for that, but as an added bonus I will have toasty hands in about any biking weather. It is a little more difficult to do the inner shifters but I'm getting better at it. These are lobsters with the index finger all by itself, those seem better for shifting than the Vulcan-greeting ones since the middle finger is what operates the small shifter and it has movement separate from the index finger. The difficulty in shifting is from how thick and stiff the gloves are as you cannot feel exactly where you are on the shifter.. the lobster finger restriction per se is not an issue.