Ive tried some supposedly waterproof rain gloves years ago, so long ago that Im sure that the technology is much better. Mine didnt work, as after an hour or whatever, my hands go wet anyway.
I do have some goretex overmitts that certainly are not waterproof, but are fantastic in fitting over various gloves and diff inner mitts and allow me to ride comfortably at -20c.
but as for rain, I've come to the conclusion that a pair of dishwashing gloves are the best answer.
Sure, one can probably find and spend 200, 300 bucks on fancy schmancy waterproof gloves that breath, and they probably work (for how many years, thats another thing....), but I am happy enough to spend that money on many days budget of a bike trip somewhere, and just put on my dumbass looking yellow dish gloves, and its ok, I'll live with clammy hands.
I have a pair of medium thin wool gloves that can fit under dish gloves, and if warmer, a thin pair of polypro gloves, so that helps with the cold, and at least not having the gross wet feeling right against my skin, and frankly, if conditions are so crappy and cold at that point, at least my damp hands are warm with the wet wool from sweating-but hey, its all about compromises, and Im fine with spending 2 bucks on dishwashing gloves or whatever, and not throwing away umpteen hundred dollars on something that takes up more space, and frankly from my experience with "wonder" fabrics, will stop working at some point---so I'll happily put the moolah towards a flight or hotels or whatever, and look like Madge from the commercials, well not Madge actually, cuz her dishsoap was so smooth and hydrating, she didnt need the damn gloves on, so I guess I look like the loser housewife who didnt use Palmolive....
hey look at that goofy looking biker honey, he's soaking in it!