It seems to be a consensus that there is no magic with rain shells. It looks similar to waterproof shoes to me, with the industry leaning heavily to the marketing hype.
Okay, assume you will get wet under your rain shell. You stop hiking and there you stand, it is 45F and you are tired and wet and starting to get chilled. Assuming that it isn't pouring, you get a dry layer out of your pack.... but UL principles lean to not carrying spares, or mid layers that might be base-layer substitutes. Oops! Many UL gear lists would have something like a Thermawrap or a light down sweater for insulation, with no spare base layer. I don't like that idea.
This is one of those scenarios where I think light fleece or other stretchy synthetic mid-layers are great. Power Stretch is my favorite, but there are tons of options, from basic 100w fleece to R1, Capilene 2/3/4 and so on. If I have stopped and find my base layer beyond redemption and I am cold, peeling and using my mid-layer for a long stop or camp would be my plan. The base layer might dry if I can get it under cover and a breeze, or a little warmth off a fire if possible. If it isn't soaked it will dry from my body heat-- if I don't get too cold trying to do that. Having a second base layer might be in the works too.
My point is that the rest of your clothing should assume that your rain gear isn't going to keep you completely dry, particularly in those scenarios where you are exposed to hours of cold drizzle and high humidity. Remember that long-term cold drizzle equals no direct sun, perhaps for days, so there is little opportunity for drying anything.
What is your solution?
Typical PNW weather: Lake Annette, Washington, July 4, 2010, 2PM PDT, elevation 3600', 49F, 95% humidity. There was a heavy rainfall a couple hours later, followed with hours of light drizzle and cold air from the snow fields above.