With the exception of a couple trips to Northern California coast and a Southern Utah/Death Valley loop, I've spent all of my backpacking and hiking over the past 12 years in the NW. I'm pretty convinced at this point that we have the most challenging conditions in the lower 48 for clothing systems. Warm enough for rain and exertion-caused heating, but cold enough for almost year-round hypothermia risk and near constant wetness.
My biggest priorities over this time have become breathability and drying time. Your umbrella idea is probably perfect, but I just don't like carrying it/giving up my poles.
In a single garment, EPIC has performed better than just about anything else I've tried. Not perfect by a long shot, but handles drizzle without a problem, breathes reasonably well, and dries faster than just about any fabric I've had. Unfortunately there are very few options out there.
I did a jacket test this past Saturday in 42 degree misty weather. 9.5 miles and 6 jackets, switching jackets every mile. Right around 18 minute miles so I was generating some heat. Of my water "resistants", the EPIC did great. Supplex also was nice, but not as water resistant and stayed a bit damp. Activent was okay - less breathable than the EPIC and heavier. Of the water "proofs", the dirt-cheap 02 rainwear was by far the most comfortable, despite some fit and feature issues. They could be fixed, though, and it's less than half the weight of anything else. Precip was comfortable, but did get some moisture condensation on the inside. My other jacket was a joke, but you're unlikely to ever see it for sale so it's not much of an option.
A really well vented EPIC jacket could be a perfect NW jacket, serving as a widnshirt and a "drizzle jacket". I've only seen one that is relatively well vented - the Feathered Friends Jackorack. Doesn't fit me, though. I'm using a slightly modified LL Bean EPIC Jacket that is no longer made and weighs 10.6 ounces in XXL Tall. That's pretty light for EPIC. I think WildThings still makes an EPIC windshirt, but not sure about coverage or venting.
I think most ideal mountain setups include a 3 ounce windshirt and a 10-14 ounce rainjacket. Usually close to a pound total in most light gear lists. An EPIC jacket (well-vented) and an O2 jacket for the super downpour would cover the NW for about the same weight. The problem isn't the heavy rain, it's the incessant damp stuff.
I've found most ultralight windshirts to be nice, but not ideal. The dampness does get to them - from the outside or the inside - and they seem clingy to me when they're wet. They do dry quickly, though. I know everybody wants to keep their ultralight windshirts under 3.5 ounces or so, but a Quantum hooded windshirt with huge #3 zip pit zippers would still be under 5 ounces and would be the most breathable thing out there. Doesn't exist unless you sew, though. I still have trouble shelling out $100 plus for these jackets, too.
BPL has had a comprehensive fabric article mentioned for a couple years no, but it apparently keeps getting pushed back. I'm curious to see a technical view from them at some point. There's some good stuff out there - Patagonia has some interesting data - but it's tough to make good comparisons.
I'm less impressed with softshells, whatever they are. If you mean the Schoeller and similar type fabrics, they're great for NW skiing, but are too heavy, too hot, and stay too wet for NW hiking in my experience. Most include quite a bit of Lycra, which I find tends to hold water. As long as it didn't get soaked it'd probbly be fine, but if that's the situation there are many other lighter, cheaper, better performing options.
Lots of blah blah there, but in a nutshell, your focus on drying time is good. Windshirts are great out here when they're dry, and softshells questionable for backpacking specific stuff in my opinion. Interested to hear what you've tried - always eager to hear what works for other Northwesterners!