As for a water-resistant down jacket - if it's warm enough to rain, you probably don't need a down jacket. Down gets its warmth from loft, and that means the fabric is probably wind-resistant but probably not water-resistant.
I thought water resistance and loft are unrelated. In the case of my sleeping bag, it uses what they call Conduit SL fabric to keep that breath in the freezing tent from turning the bag surface in front of my face into a wet sponge. My summer bag did that a few times, so I have a winter bag with the membrane fabric to keep the down dry. On a Jacket, you're probably right, there's much less of a chance for moisture to get into the fabric and melt from interior heat.
I also have a Marmot Precip for summer - fine exept that I need to treat the fabric to repel better. Clings cold and wet to your body when the rain soaks the oustide fabric.
For Winter I have a 3-layer Goretex shell, all the fancy features such as hood big enough for helmet, vents, snow skirt, etc., heavier, big enough to fit over everything but not the down jacket. But the more I think about it - there's really little point to layer over the shell, as it doesn't add much insulation (one more air pocket at best, if not compressed totally). Suppose that's what they make down sweaters for.